Please give me your honest opinion

In early December my sister had asked me to watch her kid because she had errands to run. She said she’ll drop him off at 12 and it would only take a few hours I said no problem just pick him up before 3 because I had a booked family photo shoot 5 and I had to get my kids red and drive 45 mins to the shoot

I texted her if she was on the way around 2:15 got no answer and called at 2:30 she picked me but before she said anything she said “ wait wait she’s calling me now “

I asked if she’s on the way cause it’s almost time for me to go and she said that she’s wrapping me her errands and she’ll be there the background was loud and busy like a restaurant

She didn’t get to my place till 4:36 and that point I just walked her son to the car told my kids to run in the car and sped out of my drive way. I had to pay a $300 late fee to the photographer

I told my sister that she cost me $300 for her being late and if she can at least give me $100 to cover this fee and said that she won’t give me money for being a aunt and I can’t expect her to pay she’s struggling as it is and I’m out having family photo shoots

I didn’t reply to this message and todays she called me and asked if I can watch her kid I said no I don’t want you she’ll have to ask someone else and hung up

She texted me that I’m being a selfish asshole and I’m punishing her for a mistake