E.A.
Wow. I am not even sure what to tell you except get away. Fast.
This woman apparently has problems that need dealt with. To be sure that her husband knows the extent of her online activities, you might consider printing out the e-mails and/or e-cards, if you still have them, so he can see them. The two of them probably need to get her a little counseling or something.
I would hate for your kids to lose touch with their uncle, so maybe they cana see him when she's not around... It just seems to me that she's not very stable and I would not want that around my kids for fear that her next outburst might be in real life.