most girls at 150 are overweight, even taller ones (and I'm not talking the 6 footers here lol). 4'11" and 150 is morbidly obese.
I wish I had some sage advise for ya man, but the truth is, she probably won't change until she sees a need to change that is greater than her laziness to stay the course. And she may never find that.
That is a tough spot to be in, imo.
It's a shit position to be in when you start to lose physical attraction for the person you are with, regardless of reason.
Last year me and my GF of 3 years broke up partly because of that. Obviously there was much more at play, but deep down that was one of the big issues her and I had.