what are your thoughts?

I'm 26, in school full time (summer break right now), I work full time and have a 7 year old. I'm basically going through a break up with my fiancé of 4 years (toxic relationship which I'm slowly but surely getting the courage to end). My best friend lives in Vegas and I want to go visit her for 3 days. Not to party or anything like that but simply to have my best friend by my side while I'm going through this rough time. Would I be wrong to leave my daughter with her aunt for those 3 days? She already told me she would be perfectly okay with spending the weekend with her aunt but I know my mom and soon to be ex will make me feel guilty for going. What should I do? Thank you. 
Also: I'm giving her aunt (my sister) money for everything so I wouldn't be putting her out I don't think. I never do anything for myself and I'm so sick of being controlled. I'm taking my daughter on a mini vacation this weekend to get away then visiting my best friend would be the weekend after.