Healthy eating for two? Picky partner..

As the picky eater in my relationship, what worked for us came down to making meal plans together. We started by making small adjustments to our menu options, so whole wheat pasta instead of regular, adding more veggies as a side dish. The biggest advantage is the fact that my OH has been willing to try different ways of cooking veggies as opposed to just steaming them to within an inch of their life. It isn't easy being the picky eater because you often know that your partner may be getting sick of the same dishes over and over. Eventually we reached a compromise and worked on making menus together. This way the OH can pick dishes that are more "wild" and I can make suggestions to tone it down with a small side, the same can be done on their end, say my basic spaghetti with red sauce, they can suggest a veggie on the side.
It won't be easy, but working together to create a plan, one that provideds some comfort foods (perhaps with tweaks to make them a bit healthier) but also allows for expanding the palate.
I hope that helps, I realize that it isn't any real recipes, but hopefully it can be a jumping off point for you two?

bumping because I'm in the same situation.

Also, adding that I meal plan with my boyfriend too to try to come up with something we both can eat and that has worked out so far. He doesn't have to worry about losing weight (although, clogged arteries is a different story but we're working on that one). He will not touch something that doesn't have meat in it and has a severe allergy which prevents sharing many dishes that I love. We regularly eat roasted chicken with rice and veggies; tacos (sometimes beef for him and chicken for me). I still haven't really figured out what's going to happen when I start making other dishes he can't eat. Another idea might be to cook together (to save time) making the same thing (so it fits in the budget) but each making slight variation to fit your needs (could be good bonding time too).

I'm the picky eater in my relationship. I think the important thing is for your partner to identify specific foods that 1) she absolutely hates and won't eat, 2) ones she doesn't like much, 3) ones she is fine with/tolerates, and 4) ones she loves. She may be restricting herself to mostly the number 4 category being more open to foods in categories 2 and 3 could allow for a lot more variety.

One problem I have with foods (particularly vegetables) I don't prefer is that my husband loves huge pieces. I find a lot of those foods intolerable in large pieces (like onion and bell pepper) but have little to no problem with them if they are chopped smaller and are mixed or had a chance to blend flavors with others I do enjoy like zucchini and broccoli.

If she likes cheese/dairy, then making a cheese sauce that can be put on top of vegetables might encourage her to eat more, while you could eat them without if desired.

As others have suggested, getting her involved in meal planning/shopping/cooking if she isn't already would be helpful. Encourage her to find recipes/meals that appeal to her but incorporate something important to you like a large side of vegetables. My husband and I tend to gravitate toward different recipes, but always keep the other person in mind when choosing and sometimes will actually show the recipe to the other person to make sure they are on board.

I don't know how picky she is about variety, but we make 2-3 dinners per week (off a list of approximately 30 ideas) and eat leftovers the other days. So there isn't a lot of variety within the week, but we don't eat the same thing several nights in a row. We also try to create variety week to week. So if we had steak last week, this week we will go for chicken, pork, lamb, or vegetarian; if we had soup one week, we might do pasta the next....

Of course none of this matters if she isn't willing to try.