I'm a Master student in Belgium, 2nd year, doing my Master thesis. I have a supervisor/promoter (university professor) and a PhD student as a daily mentor, we work together and get along great.
I started looking up PhD positions in and out of the country, and most positions ask for 3 referees informations. I'm an international student in Belgium, so I only knew my professors since last year, and I don't know how to ask them, I asked my current thesis supervisor and he accepted, but the other professors I was never close to them, so would it be ok to ask the daily mentor to be a referee instead? She's a PhD student in her 4th year with more than enough experience in the field.
If not, how do I even open the topic with the other professors? I don't know if they remember me. I was never an outstanding student, but I got by just fine.