Hey! I can't say with 100% certainty that this is the reason he didn't like her but from what I remember it had to do with her not agreeing with his expectations! (He didn't want to wake up with huge scars)
I do believe he said he truly loved Dr. Merten because he seemed genuine, kind, his office was beyond tidy and nice, and he focused on the chest area with his surgeries.
I really hope this helps!