I'm a huge fan of Carole Middleton, and if Kate & William make it long term, it will be due to her steadfastness and the normal family backdrop she provides for Kate and her family. I think it's safe to say she has changed more of her children's and grandchildren's nappies than Prince Charles ever has. William actually wanted to spend any time with his father, and if Prince Charles actually wanted to ever see his grandchildren, I'm sure it would happen, but the fact is that he actively chooses to spend time with his PIL's.
If Carole encouraged Kate's relationship with William over the years, then I'm sure that's no more or less than any of us would have done if our daughters met a friendly, polite and unpretentious young man with a fucked up family but strong career prospects, but I do think it's a pity she didn't push for Kate to have a career during the gap between her graduation and marriage, particularly one that she might have been able to keep a hand in (nothing springs to mind, but I'm sure there must be something - charity fundraising etc.).
I think that what is happening to Meghan Markle right now is very telling though. The engagement hasn't been announced yet, but she has given up her website (it's simply GONE), is dropping her modelling contracts, leaving her job etc. It's like her professional life is being wiped "clean" ahead of her new job as Harry's wife, which I find very unsettling, particularly as Harry never seemed all that interested in that side of being a Royal, but evidently he is.
I think Pippa is going to have a much more interesting and free life over the next 50 years than her sister or Meghan.