Sometimes it’s a case of persistence. I wouldn’t worry too much about veg that are high in sugar or calcium - spinach, baby corn, spinach and fruits.
Mine will get a lettuce leafy, a slice of pepper and a slice of cucumber daily. They also get a green bean daily if I have some in the fridge.
Sometimes it’s a case of persevering and trying daily. I would say keep trying with the bell pepper. Cut a little slither and just put it in every day. Keep putting it in every day and hopefully she will eventually understand it’s not poisonous! Try all three colours as well. My girls didn’t like celery when they moved in. I just put in a smaller portion daily and eventually they started to eat it. It isn’t my one girl’s favourite but she will eat it. I know this so I always only give her a small slice. I don’t feed it often though.
May I ask how old she is and if she lived with an older companion? Sometimes young piggies don’t know what’s safe to eat if they haven’t been in the company of older piggies that can show them the way. They can be picky eaters sometimes as well though. I just feel that given bell pepper (and coriander) are such good sources of vitamin c, I would at least persist with the bell pepper.
Good luck and hope she cottons on soon!