I feel really sad for the childhood friend. I can tell that the MC is acting the way she is around her because of her self deprecating feelings but I can imagine it must really hurt for the child hood friend. For now, we don't know exactly how the childhood friend feels about the MC and I'm keen to think that she doesn't have romantic feelings in this case. I think she just saw her as her number one friend that being close with was a constant, and when that changed she just wanted her friend back.
At least, I hope I am right. I always cheer for the childhood friend and I really hate how it is seen as typical for them to lose the romantic battle.
If she doesn't have a case of the gay for the MC then I will be very happy.