If you owe them money and especiallyif they are hurting for money, I could see why she wouldn't want you to buy anything but essentials. I could also understand where she is coming from if you say anything about being short on money or having to work extra to pay the bills. I had 2 friends I used to work with come up and we went to the casino. "Betty" and I watched "Cleo" put a $100 bill into one machine. Ok nothing said we were thinking she must be ok with what her hubby makes no problem. Over the next year she talks almost everytime about going shopping and buying clothes, ok hubby must still be making enough no problem. THEN she started to tell us how her hubby wasn't able to work as much overtime and they were thinking of getting a horse and an RV, meanwhile still shopping for clothes. Oh by the way they had just bought a nice 5 bd house. We start to get concerned because of layoffs. Then she tells us they bought the RV. They got the horse and have to board it and go every day to feed it. QVC and HSN are 2 of her favorite channels. They got 3 more dogs for a total of 5 dogs. In her next sentence she tells again of hubby getting even less overtime. A little more time passes and now hubby has no overtime and has to get second job (almost cries here) and they might loose the house she loves, but their daughter still loves her horse and might get her a second. She also tells us her father in law won't give them any money and they're all mad at him for not giving them any!
Even though these were all things that made her happy (they really didn't NEED the horse or the RV they just WANTED) we could hear that getting them anytime she wanted was hurting she and her family. "Betty" and I find it very difficult to be excited for "Cleo" now when she tells us she's getting something new. "Cleo's" finances are not our business but we do care about her. I have a feeling your SIL is just worried about you. Maybe watch what you say to her from now on about finances.