One more time, this is not and was never about the OM. He was just there when she secretly decided she was not happy and began looking for a sympathic ear. The OP is often someone at work "that understands" and benefits from encouraging her new life. In MLC, it isn't someone who represents stability and a future, cause there usually isn't one. The MLCer rejects rules, controls, stability, logic ... you get the idea. They are self medicating their condiition with fun people - people with high lifestyles, often living from payday to payday and from party to party on credit.
Hey, she's 17 again. And from her view it is what she wants and deserves. It works for her. She was not ready to be a mom. Right now she has no interest in owning a home and paying bills or being a full time mom tied down with responsiby. What career? Simply, her journey to adulthood was never a clear path and she did not have the support she desired. That damaged her. Now she's seeking her way with no idea of a destination.
You, your old friends, your old plans are logical and judgemental reminders that she'll never be 17 again. A newly emerging inner voice is constantly screaming at her "it isn't fair" and "you deserve to be happy." Only she no longer finds happiness in what she used to. She never solved inner issues she repressed since development years.
That is what you couldn't change or avoid. Neither could she. Until she confronts and resolves those issues on her own terms they will continue to consume her and all in her path. It shows in her and she's probably a long way from bottom. There's darker days ahead as this life of new revelations unravels.
Love yourself and love your son. Be thankful for the journey that served you well up until now. Embrace the positives of staying on track with your life. You can't mediate between her and her demons for her.
