I've a project manager who has worked for nearly 3 years as a recommender. For my second recommender, is it a must that I need to get from current or former direct supervisor? Since I already have a project manager, I was wondering if I can get it from peer/mentor?
Peers are usually not a top pick, unless a school specifically asks for one (eg Stanford). You can go with another direct/indirect supervisor or a mentor (could be from a group you're in or an extracurricular activity) -- as long as the person can speak about your work, your ability to work in a professional setting, etc then you're fine.
People also usually tend to shy away from professors/academics unless you're fresh out of school, youve done significant work with them outside the classroom, or there are other extenuating circumstances.
aerienWhy Yale | My Advice For Younger Applicants