The moment I smelled something fishy I would have taken the initiative. At the very next lunch, I would have looked Moochie Lady right in the eye, in front of everyone, and said "We're a little tight this week. I was hoping, since I covered you last week, you could get mine today. If you can't, I understand. Oh Suzy, I love your new jacket! Did you get it at Upscale Department Store?"
I would do this for a multitude of reasons:
1. It would show that I was not a doormat and that I absolutely expected my "friends" to reciprocate generosity.
2. It would eliminate the possibility of Moochie Lady asking me to pay after the meal was over, because I had already stated that I only had enough for myself.
3. It would prevent Moochie Lady from asking any of the other ladies to cover her meal, as the issue of her ability to pay would have been raised before the order was placed.
4. The diversion of attention to Suzy's jacket would give the impression that, of course Moochie Lady would be willing to reciprocate generosity. No one would be so rude as to assume otherwise.
And then I would order, enjoy my meal, and pay for my own lunch. Unless of course Moochie Lady offered to pay for mine. I would never raise the issue again, and I doubt Moochie would either.