Asking your parent to help pay for expenses?

My mother moved in with my husband and I 5 months ago. We have not asked her to help with any of the bills etc. and she has not offered except to chip in $20 for my cleaning lady that costs $100. This is okay, we are doing what we think is the right thing to do. However, we have asked her to cover the cost of a caregiver when we go away for a long weekend or I travel with my husband on a business trip. The cost is $100 per day. She was in shock at first but has finally agreed to do it. She's on a budget but can certainly afford this. The nest egg she does have she won't touch because she says that's our inheritance, my two brothers and I. I keep telling her that money is hers, she's still alive, and if she needs it she should spend it. Anyway.... This is much harder than my husband and I anticipated. My biggest challenge is balancing my time between my mother, my husband, and myself. Would love to hear your thoughts on the money issue....