@Camefromeurope,
This is completely INNAPPROPRIATE of her on every level!!!!! She is violating professionalism. She is violating YOU!!! You are his wife. First priority for ALL respectful women is respect the boundaries of you and your husband. She does not need to have an out of office meeting for any reason!!! Your husband should cancel, or encourage an office meeting only, or inform her, with all due respect, that he is married and does not go out to dinner with other women
If she is unhappy with that, he may consider reporting her to Human Resources, file a complaint, or find another job!
I have just been through a boundary issue myself with my boyfriend, whom I just broke up with, because he has a female friend that is too close for comfort. A respectful woman knows to respect the boundaries of another woman's man!
Let us know how it turned out.