If your friend is open to eating grilled and unseasoned fish or poultry with fresh lemon on the side, that’ll prolly meet the 
healthy requirement. Steamed plain veggies or plain salad with dressing on the side or self dressed with oil and vinegar.
The question is which Westside resto is willing to make modifications if they don’t offer such choices already.
I called Kiriko Sushi today about New Year’s Osechi dishes (they’re only doing dine-in, no takeout for the New Year’s Day menu), but I was impressed the owner chef Ken-san actually answered the phone. I suggest calling Kiriko Sushi and asking them about healthy dishes they can offer to your friend. https://www.kirikosushi.com/
One would think Watergrill or Santa Monica Seafood would be good, but I have no idea if they do dietary modifications.