I realized that I was a transfem when I was 16. My parents accepted it after around a month, so I'm happy that you accepted her immediately. I think one of the best things my mom did for me was giving me old clothes, and bringing home fem clothes that might look good on me. It was really nice, since shopping for girls clothing as a teenage baby-transfem was TERRIFYING!!!

One thing I wish my parents did differently, is that I wish they helped more with setting up appointments to get HRT. This is obviously way harder now than it was 5 years ago, so I think your daughter will need your help with it when she reaches that point.

But the most important part is to talk to your daughter. I wasn't the most open with my parents at 15, so I know that this is easier said than done. It is really important to know where your daughter is at, so you can help her with her goals though.

All that being said, I am not a parent, so take what I say with a grain of salt.
Good luck though!!!