Is my Husband hiding something?

Long story short: my husband used to work at a day carea few months ago..there was a girl there that hewas friends with named jasmine I questoned him aout her a couple of times about there friendship,nothing unusual. So I go on my husbands twitter and I see she writes him saing she misses him, and " he misses me bc he likes me" and one that really bothered me was she put " my friend (my husbands name) has a wife and a mistress #truestory lol" so I questioned him and he said it was a joke and there's nothing going on between them so I took it into my own hands and told her look I'm his wife yur disrespecting me so of course she acted like a smart *** and was being sarcastic. Then my hubby told her to "chill" I feel like he's not defending me bc all he had to say was "you said what you had to say and she said what she had to stay" where do I go from here, if he doesn't step up and puthis foot down she will continuebut he doesn't look at it that way.. adviceplease!