My MIL has reached her limit with us?

I love my MIL as a person, but she is terrible with finances, and her kids find themselves picking up most of her bills because of her poor financial planning. Right now, her 4 other kids are really struggling, but my husband and I are doing ok (by ok, I mean we can afford to live comfortably with careful budgeting, but we only make under $40k a year combined, we cannot support his moms bad decisions). Anyways, last winter, the plastic sheet things (you know, those hard, corrugated green sheets) blew off her covered porch that her 4 dogs live under. Her dogs are 100% outside dogs, always have been, they are huge, dirty, smelly, and pretty much untrained. These are not small pampered lap pets, they are just fine out in the elements. Instead of saving up to pay a professional to fix it for years to come, she assumed I would pay for the materials to do a crappy patch job that will probably blow right off again because Im not a carpenter. The monsoons are coming, so she called me up the other day and told me she needed me to come fix it asap. She can't afford the $250 materials I'll need, so guess who gets to pay? I suggested building a small wood shelter for the dogs instead, which would be just as effective and cost only about $50. But no, they have to have a whole covered porch to stay out of the rain. These dogs will be perfectly fine out in the rain come on why should I have to help them out.. If she cant afford them then she should take them to the pound right?