I came across a very old post (nearly 20 years!) online where I was referring to having recently had a first meeting with the people who would become my in-laws when I went for dinner at their house.
It did not go well.
I am a talker, and FIL, who is very quiet, found me too much. Most people think I sound fairly well-spoken but MIL is very judgemental and found me 'common'-sounding and thought I was getting ideas above my station with now-DH, even though we come from exactly the same kind of background. I know now she is someone who likes to be 'impressed' by people or 'charmed' by very specific behaviours. But unfortunately I didn't have, to her mind an impressive (read: private) education or job either, and I didn't fit her idea of a confident, socially-assertive person. A few months into our relationship, she was still trying to push him towards a private-educated girl she knew who had a City job 😅
I was both devastated and to some extent annoyed for quite some time - I'm a person who gets on with people and I didn't know what to do with someone I had to deal with who didn't like me, and I was also annoyed at her assumption I was in any way socially inferior to DH. I spent too long obsessing over how I could get her to see I was actually quite a good catch, thanks very much.
In the end it was mostly solved by us getting engaged, they accepted me at that point. I have also learned she blows hot and cold with everyone, so although I have been in the doghouse with her (usually for not reading her mind for some social rule only she adheres to) she has also said that DH did well in choosing me. I try to see the best in people and we get on most of the time, and I have learned to accept that, while she can be ridiculous in what she expects of people some of the times, and other points she does have a point and I can take it on board.