Am I also a heartless superficial slob to want her to lose the 30 pounds she recently gained? I agree if one partner is too demanding of a certain image/appearance or other attribute, then maybe the couple should split. But isn’t there room for compromise, and having some mutual health and appearance goals?
You can, of course, want someone to lose 30 pounds without being a heartless superficial slob. You can find those pounds unattractive. You can find them indicative of something else that worries you – of a stress-eating problem, of a known but unaddressed health condition, of an annoying habit of bemoaning the weight and using pre-weight-gain photographs without actually changing any habits.
You can break up with (or just not go out with) someone over any of these things.
You can also (fill in your thoughts, desires, biases, etc., here), as long as this (whatever) governs you and your behavior alone.
Occasionally in a healthy, power-balanced relationship, two people will want something different from each other, sure. But they have to approach it as equal partners, meaning basic respect for boundary lines: My feelings about you are my business, but your body and choices are yours.
The obvious answer is to just talk to my mom about it, but in past conversations of a similar vein, I could tell she felt hurt by my asking her to treat me as more of an adult. Do you have any suggestions about a light way to approach this?