Sometimes it can be easy to determine how others should spend their money

. Unless they are doing things like choosing to live in a tent in a field when they could be living in an apartment or house, I would not be that concerned. I agree with the suggestions above regarding listening sympathetically, respecting what they may have gone through in the past, and watching their numbers yourself so that you can keep track of how they are.
I am probably biased. If we had that problem with MIL, I would not call it a problem. But we have the opposite, MIL thinking she can spend without regard to what she has, and still wanting to come with schemes to try to get more.