Mom wants me to eat the same thing she wants. If I say no, she throws a tantrum. Can you relate?

Go Gray Rock - other posters can describe this process.  Basically I think you can learn to tune her out.

Your profile doesn't say ur Mom has Dementia but this is not normal behaviour. Have you mentioned this to her Doctor. She is acting like a child. She may need to be evaluated.

I really don't think you cab reason with her. Just tell her u don't care for the item or take just a taste.

Thanks.. She can eat what she wants. The thing is if I won't eat something that she wants TOGETHER with her she won't eat it ..
Throws herself and will sit and eat with the angry face on giving me the guilt trip. I can't take this!

Even when an elder has severe dementia you must set the limits. She is allowed to eat what she likes and you what you like. Just gently keep reinforcing that. Not that it will do much good because it is the disease talking, and there's no reasoning with dementia.