You shouldn't and dont care about what happened with OM and their relationship. Thats is none of your worry. Dont give him power or energy in your life about worrying why he kicked her to the curb.
She didnt show you any remorse or appreciation for helping her out. She acts like your owe her something. You are/were her rock and foundation, not her plan B. Start treating yourself like a plan A and accept no less treatment.
M:37 W:37 T:11 M:10 S17, S13, S10, S4 BD:06/28/17 OM confirmed 07/20/17 Recon the M 10/29/17 Working hard:2gether
Onward and forward
This process is not a sprint it's a marathon! Patience, Patience, Patience.