Your first question is provocative & inappropriate since Jennifer is happily married to Ben.
Your second question is simple to explain. Jennifer actually
knows both men personally, unlike outsiders like you or me.
There's either:
1. An uncompatibility between J & M that they wouldn't & shouldn't reveal to the public.
2. Ben is a better man for Jen.
3. Both #1 & #2
Jennifer loves Ben. Jennifer loves Violet. Ben loves them both. Be happy for them. They seem to have a great & happy life together.
You know, the Relationships thread is intended for the Alias Characters.