@Krbmom,
Depends on if you want to put up with her blackmailing you with her threats of sending you private communications between her and your husband.
If she send the emails and texts, you don't have to read them you know.
You can simple delete them if she decides to send, and she'll get nothing out of it.
However, you say you talk to her frequently, so what's to keep her from just vocalizing all this to you? Unless of course you cut off communication and put her off limits.
In my opinion, there's nothing that can be said between the 2 of them that hasn't already been said.