Need to vent

So ladies I need to vent my sister in law knows I work at a make up store and asked for my help with finding her makeup so I started looking for make up for her but had to work on some stuff so I didn’t reply for a few hours the next text I get is her asking if I have one of the stores cards which I said I do because I work there she then went on to ask me if I could buy her stuff and she just make me payments back of what she owes me because she didn’t want her bf to find out. She sent me pics of how much it was she wanted to charge to my card $617.02. Which my fiancé told her to tell her no which I plan on doing but was frustrated she asked me then went on to ask my fiancé to pay for it. She already has multiple cards open in his name that she barely pays on. It frustrates me because my fiancé and I work hard for what we have and have worked hard to get to where we are in our jobs and money wise. Do you think I have a right to be frustrated?