You can't make her be, or not be, anything perhaps parental influence is limited. But social contagion is real and detransitioners talk about the influence the internet, and sometimes, older trans people, have on them.
So gender non conforming DC can be made trans, who wouldn't have been in different circumstances.
If my child thought they were trans, I'd be doing everything I could to support them through the next few years so they have a chance to grow out of it. (Puberty is the "cure" for trans, for the vast majority of teen trans kids).
Spooksandchocolatecake I've read detransitioners talk about what pulled them out of the trans bubble (as well as growing up generally) was reconnecting with the outside world, not being in that bubble all the time. Does your DD spend a lot of time online? Is there anything she enjoys in real life, that you might be able to encourage her doing, to keep her with at least one foot in the real world?
Don't force her to say she's trans, as that makes it harder for her to backtrack.
If it was my DD, I'd be ringing up my butch lesbian mates I haven't seen in a while (as we moved) and asking if we could spend some time together, to make sure my DD has some positive lesbian role models in her life, in case the issue is that she's struggling with her sexuality in a homophobic world.
Don't, whatever you do, invite Mermaids into your life (that's a fast track to medical transition) or let her see any therapist who believes in affirmation.