What would you do? Friends kid is a brat

I have a good friend I get along great with she has a 3 year old son and I have a son who will be 2 years old next month anyways everything was going great we talk a lot and it was nice having someone to go do kid stuff with but then she started asking me to watch her son for her some Sunday’s which I said was fine I’ve never watched anyone else’s kid before but figured couldn’t be to hard and then I found out she was working 5 hour shifts and was paying me 20$ to watch him whatever she’s my friend I’d love to help but then her kid is HORRIBLE at sharing and listening and just a number of things that makes it very hard to deal with and at first I didn’t tell her because I didn’t want to ruin our friendship or anything but then last time I could t take it he was being so mean to my son not listening to anything I’d say she let him bring. His toys over but he wouldn’t share them with my son at all and he would also not share my sons own toys with him and would come rip toys out of my kids hands and it was a lot to deal with 5 hours felt like forever I get some toddlers have bad days my son isn’t always perfect but he’s a fairly easy kid to deal with I’d say and so I had to tell her about it and now I just can’t take the kid much I don’t like how he acts and treats my son and she doesn’t do much about it when we are together like he was hitting my son with a toy once in my car and I told her so she could handle it and she said that he couldn’t have the toy if he was going to hit my son he threw a huge fit so she gave it back to him and was like ok you can have it then just don’t hit I’m trying not to judge but it’s so hard and I really like her as a person but now hers the problem I made plans with her out of town for the 4th a over night trip and now I don’t want to go be because I don’t want to get stressed out because of her son and how he acts and how she handles it (which is not at all really) but she’s made all these arrangements and taken off work and I know if I don’t go she won’t go and I just feel bad but at the same time I’m not wanting to be stuck in another town on the holiday miserable and annoyed the whole 4th plus I don’t want my son to suffer I’m afraid if I cancel that night be the end of friendship especially since I eel like things aren’t the same since I told her how her kid was acting and that he has a lot of issues with sharing I think she took it personally what would you do