Long story but my DH has a difficult relationship with his sister. She is a single mum who takes the piss with childcare and financial support from my MIL. She goes out into town most weekends with MIL babysitting. She goes on holidays to Ibiza/Spain with her friends and her 7yo son has never been on holiday. We live in a different country so can't help out physically so DH feels extreme guilty that his mother is left to do everything.
SIL was made redundant in the summer and still has no work. MIL is paying mortgage for her and we have just found out she has also paid off the £8k car loan that SIL in had.
My DH thinks we should step in and help pay. If SIL were grateful or this was a once off I would not mind but he has helped her out with money in the past and nothing changes. I feel like we are just reinforcing her behaviour if we step in and help... AIBU??