Stepchild's Vision Expenses

Last week, I wrote about hemorrhaging money to the ex after receiving a bill that included unnecessary expenses on it for my stepdaughter. Usually, we've paid them in the past. This time, I set it on my husband's desk and waited for him to say something about it. I wasn't too keen on putting out money right now because:

1. We don't have it. Our house payment is late this month and we have a $702 propane bill that is due in a week as well.
2. We paid extra the last time for more expensive frames, that was an unnecessary expense because our insurance does cover frames to a certain amount. The ex and my stepdaughter decided between them to go over. We didn't HAVE to pay it, but we did anyway.
3. I thought to myself: Would I have done this for one of my own children? The answer to that is no, not if we didn't have the money. Times are hard and we live on a very tight budget that leaves little room for anything extra right now. Everybody has to "make do" and that doesn't change because two of the kids live with their mother, who gets more money from us in support for two children than we spend on our own four children.
4. I am way behind in scheduling my own eye appointment, putting it off beyond when I should have because we didn't have the money. If I can't afford new glasses, that this almost blind old bat needed months ago, why would I pay unnecessary vision expenses for somebody else? I wouldn't.

Anyway, my husband asked me this morning what I thought we should do about it. I gave him the reasons above (reason #1, #2 & #4) and he was agreeable. I did compromise and told him that we would pay the necessary vision portion of it, as we should and have always done, and if we have the extra money down the road, then we would send it to the ex for the unnecessary expense. It's not like she asked my husband BEFORE she spent the extra money if it was something he'd be agreeable to and it's not like the ex or stepdaughter would be appreciative of it anyway.