i know what your gf is going through becos i see smses from girls all the time in my dear husband's hp.
i dont't think the problem is that she doesn't want him to contact her. i think she is unhappy that they are that close.
i'm sure you understand what i mean when i say that women treat emotional fidelity very seriously. the fact that her hubby is so close with his colleague shows that he is sharing parts of himself with another woman. your gf feels threatened.
maybe what she needs to do is explain to her hubby that she is just unhappy that they're too emotionally close. this kind of intimacy should only belong to a wife. anyway why should a husband complain to another woman about his unhappiness? what is his wife for?
that said, that doesn't mean they can't be friends. joke in office, go for lunch, tok cock is fine. but not to get too personal .
just my 2 cents worth.