If you know she has OM, do not let her have her cake and eat it too. That is her total MO with you.
She deserves no part of you in any form so long as she has an OM in the picture, and you giving her any part of yourself now is getting in the way of her missing and valuing you.
Taking you out to a meal? Oh, hell no.
Listen, ex-W, I'm moving forward with my life. Please don't call me anymore unless it's an emergency related to the kids. Thanks, hope you're doing well.
Then don't answer any of her calls. If she is interested in finding a way to reconcile, she will find a way to communicate it to you. I cannot count how many of my W's calls/msgs I did not answer or return before we reconciled (hundreds, there would be multiple calls and hang ups and texts on many days). The first time I called her back was when she said she left a msg saying she wanted to meet up and talk about trying again. That was after multiple months of no no answered or returned calls. As far as she was concerned, I was on her hook, her Plan B, waiting in the wings until that happened.