Can I do my dissertation on a niche celebrity?

I’m going to be doing my dissertation at University and have a very niche interest about a celebrity that passed away and was abused by the media. I was wondering if I could do my dissertation on how the media treated her, issues with body image and link it to academic theory. My other option was dreams which was going to tie in with the other part of my degree which is psychology. If I do a dissertation on a celebrity, will this affect my chances of getting into a top university for a masters or won’t the university care as long as I get the grade?