I would be upset if my other half's mom didn't like me, not to mention the other ex. Secrets aren't good when one has had a long standing relationship.
And Sara does know Ray very well, she's worked with him since S/9, and they are fantastic together..She prefers a more mature man who's had lives experiences, such as him. She is friends with Nick and Greg and the rest, but with him and her have some common issues that they share which the other team doesn't. Different strokes for..... you know the rest.