My (31M) GF (30F) keeps saying she wants to lose weight but doesn’t do anything about it?

So my gf was in pretty decent shape when I first met her over a year ago. I’m a very skinny guy myself but I also work out and I’m decently muscular for being so skinny. I’m 5’11 145lbs. Not really considered underweight anywhere else but America (where I live). I tend to smack a lot and eat a good amount to keep my weight up while also working out but then that might cause my gf to do the same and she just doesn’t have my metabolism. She has gained plenty of weight since I met her. Weighing maybe 135 or more while being way way shorter than me and at this rate she will be my weight soon.

It does bother me a bit as I worry she will be heavy and less attractive after we marry despite me still finding her attractive and not really “fat” now despite the weight gain. I suggest we work out together all the time but she has this gym phobia based on nothing really especially since my gym is Planet Fitness a cheap gym that literally has judgement free zone written in the walls and plenty of out of shape people work out at constantly only coming once a week or month. Still she won’t come or change her diet. She hates veggies of all kinds of nearly anything healthy. But she gets so upset she can’t fit into any of her old pants and even the new ones she had bought the last time she couldn’t fit into her pants.

I feel terrible reminding her of things like we need to work out or pushing her to do anything healthy as it sounds like I’m calling her fat. Still I admit I’m afraid of losing attraction should she actually get “fat” if she surpasses my weight one day. How can I be nice about it? I try getting her to jog with me. We’ve done some Netflix workouts inside but we barely have the space for all that and it’s not routine enough. I feel part of it is my fault since neither of us cook and she lives at home but I’ve lived in my own many years so I’m used to eating out a lot or getting fast food and also snacking.