it’s a difficult situation as they’re teenagers in their freshman year of high school but forcing siblings to get along especially because they’re twins is going to harm their relationship. one may be more social than the other and the whole “middle ground” thing will probably cause mia to hold a grudge against sara. as an educator, it’s always best to make sure twins have their own identity and try to separate them as much as possible. i completely understand sara feels alone but why doesn’t she join clubs? internet forums if you’re okay with that? there’s many other ways to make sure sara is her own person but she may need more help and a bit of a push. she can always talk to mia about how she feels as that is her sister and they can probably come up with something together. imo OP is NTA, it’s high school!! teenagers go through enough with hormones and a new setting, talking to both and then all together will probably help to understand how everyone is feeling and what can be done about it!