My 99 also doesn't know econ is very worse. She went to a few long+short haul trips in these 2 mths. She normally expects my hubby to treat her, however, as econ is that worse, my hubby only gave her a few hundreds for petty cash, she paid all the trips herself.
You should tell your 99 abt your finance situation. You are a 1 big family ma, she would understand.
If your husband give living expenses to her (your 99) monthly, then ask her to pay for herself.
If your husband haven't given $ to her, then I think even you pay for her daily (e.g. $100 each time), there are only 3k per month. It is less then the living expenses your husband should pay for her.