Welcome to the forum!
I can only agree with Linky and SB! Cal will eat ANYTHING if she is out of the cage and mum is eating it. This is why I have been put on an unconcious diet. Cal is WAY quicker than me if I am eating a cheeky bag of crisps so I don't lol.
It may sound silly, but if she enjoys sharing from your cup, get a smaller cup and put some fruit in it for your bird to pick out?
What fruit and veg have you tried?
I find Cal my sun conure loves peas and sweetcorn most in veg as she eats the inside and drops the "shell". She eats broccolli and cauliflower by pulling the tops off and also peels the stalks like a cheese string! Additionally, I buy frozen spinich which is frozen in little blocks. When this is microwaved it all breaks up and covers all of the other veg giving her much needed vit K whether she wants it or not!!!! Additionally she will eat carrot, kale and green cabbage.
With fruit I have been very adventurous. I have trawled the supermarkets to find her exotic fruits. What is her favourite? Apple and grape lol. Peeled and broken down into small chunks. She also likes melon, pineapple, cranberries and occasionally fresh coconut. To name a few!
She also enjoys oatmeal, the occasional meal worm (eew I know), boiled eggs....
I would suggest trying everything you possibly can and failing that, some fruit juice in her water will get her to have a taste for things. Most sunnies dislike oranges etc but it sounds like yours has aquired tastes already!
Good luck!