I am currently in the process of applying to the Babson Graduate program, which I've decided is the only program I am going to apply to for a variety of reasons. My GREs are done, transcripts sent, resume uploaded, and am deep into the process of essay writing. The only thing I'm still a little unsure of is my second letter of recommendation.

I completed my undergrad degree in architecture in spring 2010, which included 3 co-op positions in the architecture field. Since then I have been working in a small construction management office as an assistant project manager. The owner of the company works with me directly on a daily basis. We have a good relationship and he has agreed to write a letter of recommendation for me.

I cannot decide, however, on who to ask to write the second one. I am planning on a career change moving out of architecture. My options are the following:

1) Another project manager at my company, though they're letter would probably be very similar to the first one
2) A previous employer at the architecture firm I most recently co-oped at, which was a junior designer, not a leadership position, and it was for 6 months 3 years ago. That employer also briefly worked with me when I organized a student event the following spring, however we have not been in touch since.
3) A previous teacher who I had a wonderful relationship and have sporadically kept in touch with, though her insight would be more focused on my abilities as a designer and student.
4) A peer who I have known throughout architecture school and am still close friends with. She was involved in both the student groups that I organized and led in undergrad, and the current start up that I am working on as well as having insight into my overall personality.

Thoughts? None of them is perfect, but is there one that is best?
Thanks so much in advance.