Looking For An Ally
Aside from the Fab Four’s feud, let us not forget the bad blood between Kate and Meghan. When Meghan officially became a part of the royal family, she probably thought that she was going to be close and find a partner in her sister-in-law.
Too Busy
When Meghan became a part of the royal family, Kate was pregnant with Louis and probably had no idea that she was supposed to assist Meghan out and help her with the adjustment. Since Kate had things to deal with on her own, she did not have any more room to deal with other’s problems. This can be the reason why Meghan felt she was being treated coldly.