Lady Diana Spencer and Lady Elizabeth Bowes-Lyon ( the Queen Mother) were aristocrats as their father’s were earls. ( See Downtown Abbey)
Camilla is fairly well connected. I just googled her, and she is the daughter of a Major and granddaughter of a Baronet, as well as being a great granddaughter of a former mistress of King Edward VII. So aristocratic without being titled.
Although that means nothing as some people are great grandsons of baronets and have grandfathers who went to Eton but aren't in the least bit posh now. OK that's my husband.
So it can go either way.
Diana was from a more aristocratic background than the royals technically, because the Spencers are a far older English family than the current RF and were instrumental in putting the current royals on the throne to avoid Catholicism taking over with the Stewarts who were actually in line (I think, someone can correct me if I've got this wrong).
When I lived in The Netherlands, a Dutch person told me that the Dutch (Queen Beartrix in particular, and the Swedish, Norwegian and Danish) royal families looked down upon the British RF for being a bit nouveau riche because of this and that they wouldn't want any of their children marrying into the British RF as they had a reputation for being crazy and not treating people who married into them well. Whether that's true or not, I couldn't say.