Reference question: stuck on 3rd reference

[Allthegoodusernamesaregone]

Hi all!

I've been overthinking who to pick as my 3rd reference and I've wasted so much time debating what to do and I realise I need to send it out asap! I'd appreciate any insight!

A little bit about me...I was a student, TA, RA, lab manager and currently doing a research project all with the same professor, and that's one of my references. While I know she would give me a really solid reference, I feel limited in my references because I feel most people have these (or similar) experiences spread across multiple people but most of my experiences were with her. My 2nd reference is a strong reference for a volunteer position (non-medical setting, I founded & direct a children's program at church).

Now my dilemma:

Option A: Grad student in the lab
- The Grad student observed me work as an RA and grow in this position to become the lab manager, he was the lead TA for the course I was TA-ing, we've worked closely in the past 2 years, he's observed how I work in a team setting (more often than my prof), he's sort of the"middle management" between the prof and I, and he cares about my future goals

- BUT, I worry this might come across as redundant, or even a "red flag" that I have two people addressing my work for the same positions or that it looks like I don't have anyone else to talk about me.

Option B: Volunteer Co-ordinator at hospital

- I moved away from the city where the hospital was, so it has been over a year since I volunteered there. I remember her being overall satisfied with my work and liking me, but she did not really observe me "in action" so doesn't know me too well and honestly probably doesn't really care/ isn't too enthusiastic about completing this.

- BUT, it is in a medical setting and might be "safer" if option B is redundant/concerning

Thank you SO much for any help with this! I really appreciate any insight.

tl;dr: strong (but might be seen redundant/red flag) reference from Grad student who's mentored me and worked closely with me vs weak generic reference from volunteer coordinator?