((Well, you shouldn’t outright throw food away. If possible, you should save it for someone who would eat it. You could make suggestions for dinner sometimes like “Hey, spaghetti sounds pretty good one of these nights”. You could also request that your portion not be made with beans but rice or potatoes instead. Or, if you’re able to, make yourself some eggs or something else for dinner when the beans are being served.
I can’t say much about the relationship you have with your mom, since I don’t know either of you very well. These are just some suggestions. I hope it helps.