Your LOR doesn't have to be from a pharmacist but it can't be from family or friends. It can be from a professor who knows you well from undergrad or other professional organizations.
What if there's no professor who knows me well but i asked a professor in a class I did well in? The letter is mediocre though :/
What does your mentor do? If they can talk about your work ethic and how you've applied that to your academics and extra curricular, I think that'd be good. I also suggest that if the mentor can talk about your passions and how you've acted on them through your extracurricular activities, that'd also be good. Ask them to be careful with their wording. Some schools specifically don't want a letter from a mentor.
I think having her letter would be good because maybe she could talk about your professionalism or something
Hmm, that letter won't hold as much value I think because your mentor is technically a classmate/friend. I thought that she was a mentor in your retail job. Do you have anyone that has seen you in a professional capacity that can write you a letter? Even a TA for your undergrad courses would work!