chiming in as an autistic and bi adult - it is common for us, boys and girls, to feel disconnected from socialized gender roles and to be lgbt or asexual. we tend to like styles that are comfortable, no matter what we identify as gender-wise, which may include tomboy dressing prefferences. more time and progressing through puberty will help clarify her sexual prefferences whatever they may be. no one can stop her from being herself on the inside, but shame can stifle her and make her feel like she needs to hide her true self. even nonautistic people waver on this decision for themselves and can take a long time to feel comfortable in their skin. it's great that you're here asking about it, and I hope you're not against taking advice from a non parent.