My advice depends on what you want to have happen. If you want to embarrass her b/c you think she's being deliberately inappropriate then 1. Talk to your wife & let her know, 2. Bring up one of her more tasteless jokes *in the presence of your wife*: "Yea, hon, that reminds me of the jokes that xxx has been emailing me (give example)". That should do it.
Or, if you are feeling kinder, you can just IGNORE the jokes. Don't even respond with 'lol'. Just delete them as they come in. Ppl who seek attention give up if they aren't getting what they want.
I have friends (some male) who sometimes send jokes to me. Occassionally, I send a 'reply to all' which includes my husbands email address. Just to let anyone who might be testing the waters know that I communicate w/my husband about these things. Keeps it all 'above board', you know?
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh