I offered to buy my co-worker a coffee and she ordered a really expensive drink. I'm irritated with her right now.
Why are you so bothered by the drink she ordered?
It was really expensive! When someone offers to buy you something, you should order something reasonably priced. I don't have a lot of disposable income.
I can understand you're frustration. Maybe she didn't understand that you were limited financially? I'm sure it was an innocent mistake.
Maybe it was, but I she's always trying to take advantage of people.
I would be frustrated by this too. It might be best not to offer to pay for her coffee again if you're working with a limited budget. I know you were trying to be nice but you don't want to strain your budget.