Thanks everyone for the great advice! The point of the question was exactly how I can justify picking up someone else without going into all this drama nd making a "poor thing" impression 'cause it's far from who I am. That just happened, and we all got over it. My former chief would surely promise to write a perfect letter, but she might end up not doing that. So, I wouldn't risk. I am pretty much sure MBA is what I need at this point of my life: I am ready, have enough of experience, and motivated. It is not a huge problem to find other people to give positive recommendations: I have clients (working freelance as a biomed consultant for newspapers and even one project at the TV and as a translator/writer), PhD advisor, advisor of the scholarship program for talented med students, etc. The only thing is that they all are not MOST RECENT. As far as I am concerned that's kind of a stain on the application.