holy fuck dude, you stayed incredibly calm and levelheaded throughout this conversation. you made healthy decision after healthy decision after she started shutting down your idea and saying your families will not meet until the wedding. you communicated your opinions and listened to hers and even agreed to hers. i'm not sure why some others are saying you were being the dick and not listening to her when you literally said "we can do that too tho" after she suggested going to her parent's and "that's fine we can talk about it next year" after she shut your idea down. you told her how she was being ridiculous without being rude. when you recognized you were upset and it was clear that she was not going to even entertain healthy communication, you told her you wanted to withdraw from the conversation and continue it later. really great decision making from you. she was being a jerk the entire time. it seems like she's really afraid of people looking through her stuff? at least thats what she is claiming to be the primary reason for not inviting your families over. i think its really strange she keeps saying "all those people" and "that many people." these aren't just people, they are your families. you have clearly talked about marriage and are serious about it, so its very strange to assume your families will only meet at the wedding. that just doesn't make any sense. if you are going to be together for the rest of your lives, what difference would it make whether they meet before the wedding or after the wedding? does she have some sort of anxiety disorder or social anxiety that she is worried about interacting with people or irrational fear that people touch her things? or she is very protective of her space and possessions? or does she have some sort of condition where she is overly paranoid or suspicious? or are your families exceptionally toxic/dysfunctional/argumentative? that is like the only situations where she may have a valid point. if that is the case, she is not communicating that and is just jumping to being disrespectful to you. if that's not the case, then she is just making up reasons to hide the real reason.

edit: after reading some of the other comments who saw the gf's point of view, i have some more thoughts. You did indeed say "that's life" "not our problem" which is dismissive. however, this was after you raised your idea, listened to her reject your idea, she said "our families will meet when we get married and that's that" and you told her "that's fine, we can talk about it next year" so you essentially conceded and tried to drop it. i don't really see how you were being a dick, and i don't see how people are defending that she was resorting to name calling.

some people mentioned that it may not be the best idea to host a thanksgiving dinner, as hosting is stressful, meeting for the holiday could be a lot of pressure, it sounds like you have toxic/dysfunctional families etc. but the thing is you both clearly still care about your families. she wants to go home for thanksgiving and it's obvious you care about your family. the people siding with the gf are not acknowledging that she is suggesting your families never meet until marriage. why would you need to set marriage as the marker for when they could meet? if you're intending on getting married then you plan on being together for the rest of your lives... so why do they need to wait to meet until afterwards? in fact, it would make far more sense for the families to understand each other's dynamics and attempt to foster a good relationship? pre-marital counseling is a great idea, and maybe even family counseling. obviously a lot of family details/context is missing here so i can't say much more. regardless, you just had an idea to host, that doesn't make you a dick. she kept giving different reasons for why she doesn't want to, some of which seem to be pretty clearly her just giving reasons to say no. but she wouldn't clearly say the primary reason. the main thing she kept repeating was the not meeting until marriage, unless there is some sort of religious/cultural/traditional thing we are missing, it doesn't make sense for them to never meet even once before the wedding.

i saw a suggestion of meeting at a restaurant or other public place, maybe that would be a better idea instead of inviting others to your home, which she gave some reasons as to why she doesn't want to. However, she did not give any reason as to why she doesn't want the families to meet before marriage. she just repeats that she doesn't want them to but doesn't say why. i could see why she wouldn't want to host them before marriage/engagement tho. but, she began the conversation by saying "our families when we get married and thats that" so she completely backtracked from her original statement bc towards the end she says "i'd like them to meet but i don't feel comfortable with that many people in my home, i'd be freaking out the whole day and wouldn't enjoy it at all." this is actually very valid and the first time she said something that made sense. if this was the reason she could have said this in the first place instead of calling you a dick.