My children are still pretty young. My oldest is 13 and he isn't at all interested in girls yet (He's autistic). My oldest daughter is 12 and she's the one that's starting to show attraction to others. The biggest problem we've faced so far with her is that the little group of friends she has are all into this whole "bi and gay" junk. So naturally my daughter comes in from school one day and tells us that she likes another girl. I honestly don't even know how to handle that. Thankfully she lost focus on that and got into band instead however, I still don't know what to do exactly when/if this same sex thing happens again in the future.
My advice, for what it's worth, would be to spend time in conversation with her. When the subject of LGBTQ etc. comes up ask how much she has found out about it all so far and listen much more than you talk. Find out what she has discovered so far about the whole subject and range of human sexual orientation and relationships. Help to affirm her in her own God given identity, the one that you know and love and is still developing. If you get the opportunity, and if she is interested, tell her about your own experiences during your adolescent years. Don't try to indoctrinate her. Befriend her, affirm her and gently guide her. Non judgmentally do what Jesus would do for her, fulfil her need to be understood and appreciated as a person. .
I think Tiffy's advice is sound. I think what's also important to appreciate is your daughter is still only twelve. She cannot really understand the concept of sexuality fully, let alone her own sexuality. It might be time to talk to her and ask why she thinks she 'likes' anyone, and help her understand the emotions she is experiencing. If she expresses an experience you would agree sounds like romantic attraction then don't be harsh or judgemental - she's twelve. If you want to have any influence on her development in this way she needs to trust you and feel comfortable talking to you as her experiences become more serious in later adolescence. As out-of-t0uch as it might sound to say "she'll grow out of it", she definitely could still grow out of it. Steer her how you think appropriate as her parent, but appreciate there's really only so much power you have over your children, and your actions can always push her strongly into a more radical LGBTI camp than her friends circle (online or otherwise), in the pursuit of a community that accepts her, and that's going to be less healthy for her mental health.
It's normal for children to feel platonic friendship attractions. I suspect that modern society's sexual messaging, modeled by characters in movies, games, etc., has confused children and teens to the point that they don't know how to separate platonic feelings from the romantic feelings they see modeled.
I really recommend that you completely surround yourself with Christian/traditional families. And I do mean, completely surround. A person is an average of 5-6 six people around them. Even one bad apple around your children means a huge threat to their moral and spiritual formation. It's no joke. A person is not an average of "50" or "100 people around them"; it really is just 5-6 people, as studies (and all of human history) have shown. One is all it takes to permanently impact a child. Two bad apples will break the child.
In my experience, as a still sort-of young person, when young Christians are alone outside the view of their parents they're no less prone to promiscuity, drug use, homosexuality or any other types of behaviours that might concern a Christian family. You're absolutely right that you should want your kids to hang out with moral, motivated people, but just assessing it solely or even predominantly on the basis of a families faith is unlikely to be a reliable way to do so. In my personal circle of acquaintances the kids from the most devout RC family I know are all universally rebellious the second they're alone. I don't think they'll continue going to church or even pretend to be people of faith once they move out of home. One of the kids I know is gay, and is a regular attendee of their Universities 'Queer Collective' meetings without their families knowledge. If you met them in a family context you would swear they're hardcore Catholic fundamentalists and love to have your kids spend time around them (or maybe not, but for different spiritual reasons). Perhaps at the youngest ages devout families have consistently prim children, but I think it's unlikely any pre-teen child is going to 'corrupt' their friends - morally or spiritually. What you really need to look out for is their influences in high school and university. Obviously some bad influences are easy to spot, and all parents have an instinct to sort that out, but most are hard to tell at a cursory birds-eye glance. A kid from a 'traditional' family is not really any safer a bet than anyone else from their school. If your children trust you they will listen to how you guide them. Hopefully that means they'll know what friends to cut off and what new friends are healthy to hang out with, because they'll know who their friends actually are when not around adults. Good communication and a strong relationship of trust, where your children feel comfortable telling you everything about their lives, is the best way to determine who are the good and bad influences - or at least a more sure way than how their family looks from the outside.
Proverbs 22:6 is idealistic. "Train up a child in the way he should go" and you'll improve the odds that he won't depart from it, but no guarantees!
I'd be extremely careful and cautious how you handle this and it seems to me you did it in a good way. When children are that age (I've had three who've been that age) something they're absolutely crazy about today is ancient history next week. We learnt not to get too worried about our children's latest thing because we gradually learnt whilst we were still worried about it they'd moved on to something else. One of the problems young people have at this age is their bodies and minds are changing but they don't know how to respond to those changes. Of course peer-presure is great and you need to carefully monitor it without being too obvious about it. If you're too strict and too obvious their response is to hide it from you and they can be very good at this. Remember they spend many hours each day outside of your sight and control. Because their bodies and minds are changing they cannot always understand their feelings. Your daughter may have particularly liked a girl she is friends with. This can develop into a crush. It doesn't mean that your daughter is homosexual. It may not be long before you're worried about the boys calling round. The key thing is to ensure your child knows that with you they're loved and safe. Despite how uncomfortable you may feel you must be open to discuss anything with your child. Unless it becomes a safeguarding issue you should often allow your child to begin discussions. To young people of your daughter's age it is "gross" for adults to mention sex and we certainly mustn't be doing it. We have one child in her very late teens and two in their twenties. Trust me it does get better. The stroppy teens do come to an end. Your children, you will find, do actually turn out to be quite nice people.