I agree. Why would you set yourself up for a stressful situation living with people you don't really like and who may not like you? That's just a tense house and no way to live. I would think about how you can have your own place with your partner. Couples need their own space rather than lots of extra people around.
In general though, yes. I would greet people I like with to be polite each morning. I say good morning to my kids each morning when I first see them. Or when someone comes home I say hi to them.
It's indicative of the status of your relationship that this is a problem.
I would see about a new job, job training, college or 'something' to help get you and your partner in a better financial place so that roommates are unnecessary and you can have a peaceful home the two of you. good luck
It's never a good idea to plan to live with people you don't get along with, and don't plan to try to get along.
Is there somewhere else she can go? If you need a roommate for money purposes, can you get another one?
Or better, can you make the decision to find things about her you like and try to overlook your differences?
If tou dont say it to anyone else why say it to her? Especially if you dont get along.. to say it wouldn't be rude it would be phony Lol i mean if she says it to you say it back cause then it would be rude lol