It sounds like this is an emotional time for you, both the happy and the hurt emotions. It's probably somewhat emotional for M2 as well. I can't tell as much for M1, although she is kind of in the middleman position and it might be stressful for her to try to balance things between you and M2. You're kind of in a V situation at the moment (or an "emotional triad"), but a "full-on" triad might be in your future as you and M2 spend time together. I would suggest at least spending some platonic one-on-one time with M2, perhaps in a "girl's night out" setting.
Mainly, if you'll continue to take things in small steps, and talk with each other, and keep the communication flowing, you'll come out fine, and things will gradually get easier.
I send you my best wishes.
Love means never having to say, "Put down that meat cleaver!"