Boyfriend and Bestfriend

My bestfriend and I have been bestfriends for 7 years, a super strong friendship. So my boyfriend has recently left his home and has been staying with friends and just trying to make ends meet day by day and my bestfriend asked if I can go to hang out with her but I said that I might be with my boyfriend and she got super upset and kind of put her feelings before mine and then after I explained to her that I should be there to support my boyfriend during this very difficult for him, she hasn’t answered me back. I understand that she is upset but I feel that it isn’t fair that the one time I have to be there for my boyfriend she doesn’t find that okay. How should I react to this?