it's a hard balance to pull back, i guess i see in her mind what is too far. i have not been mean or an ass, but compared with the old me, i was shorter with conversation, did not check in with her and have not been doing things that she can pay for.
Make your conversations with her less FREQUENT, but also try to make the conversations that you DO have (just so long as they're not R convos) real good ones -- be a great listener, be charming, interesting, engaged. When she sees you talking to other people, be similarly charming and engaging and empathetic.
I do NOT think you should pay for things that she is capable of paying for, and don't pay for ANYTHING that enables her affair.
