Last minute invite for family gatherings

Sometimes they don't invite us and when they do it's at last minute. One time this lady (friends with my Aunt and my Mom) asked my Mom if she was going to my cousins graduation party, my Mom and me had no idea about the party, well apparently everyone except us were invited and guess what? We got invited last minute. My Mom and me were so hurt, It feels like they don't respect us and every time my bf shows up my cousin makes a face when he's around.

When they invited us to a bday was back in March, my cousin was handing out food and she practically threw the plate on the table like as if my bf was a dog, I can tell he was very angry and didn't eat because of how rude she was to him, he didn't say anything because he didn't want to make a scene. My cousin has even told me "not to bring him around" which is not fair because she dates her own damn cousin! Everyone in the family knows they have been dating except her Mom. We have gotten into it before because of her attitude, she is very stubborn and bitter, yet nobody puts her on check because of how she is. Well today we got a text message (thread) my sister in law and my niece included this morning, again last minute invite for Thanksgiving, which my Mom and I declined to go and made it clear "we had plans a month in advance and we can't be waiting a day before a holiday" Usually for Thanksgiving they use to ask us what we're bringing and it just seems like they don't want us around and if we do go it will be awkward at this point with my cousin making a face. My bf says I'm too nice to her and that she is jealous of me and my accomplishments in life and that I need to put my foot down. I'm just sad and disappointed and it really affected me (health wise; depressed, sad and guilty) and my Mom because we all grew up together and now nobody calls us now. For Thanksgiving we're spending it with my bf family which we are very excited to attend.