What would you do if you had/have a friend that is so obsessed with their romantic partner, that they get so defensive?

For example, if you haven't met their romantic partner yet and than you say something like"I hope he/she is nice." And they get all defensive and say,"what do you mean, of course she/he is." And they get a defensive tone or you make a joke about their partner and they react like a baby. And the joke wasn't a feb offensive. Like extreme obsession that you feel you are walking on eggshells with the friendship.

What would you do if you had/have a friend that is so obsessed with their romantic partner, that they get so defensive?
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