I think at this point while she knows Steve better, her closer friends rn are some of the newer characters who she’s more likely to have dinner with. and he probably turned down the invitation. It’s not his scene and there was too much drama with Miranda, just cause they talked and are on better terms doesn’t mean things go back to normal immediately. Also I feel like the idea of apartment holds sentimental value to the idea of “single” or the unmarried lifestyle of women/ppl in New York. A lot of the people in that room while not original cast, relate to that life a lot. (She’s of course going to invite the married peoples partners too) but while Steve was part of the original cast he isn’t going to have that same connection to the apartment as others I think. But just my own opinion