While not a female, let me offer you some advice about dealing with women.
NEVER say anything about how a woman looks, or what she looks like in a derogatory manner ever. Even as a joke. No jokes about her ass, or looking like an animal, or any of that. When it comes to insults, women are like elephants... Er, did I just type that? Whoops.
By elephants I mean they don't forget. They may claim you're forgiven, but when you **** up they'll be there waiting to rattle off the list of every thing you've ever done wrong by her from joking about her ass to that time you purchased her a strawberry milkshake because that's what she told you, but you should have known that she wanted chocolate.
Women basically communicate on a whole different level of subtlety. Her mouse comment was to say you look cute. Most people do not find pigs attractive. In fact, when a common phrase used to be derogatory towards women is "look at that porker..." Well, you dug yourself in deep.
So, take it from me. Ixnay on the you look like a <negative>... EVER. You'll go far on this advice alone. Doesn't matter if she actually has put on weight, she already knows that she has and she wants your assurance that she looks good.
"Well, then," the Cat went on, "you see a dog growls when it's angry, and wags its tail when it's pleased. Now I growl when I'm pleased, and wag my tail when I'm angry. Therefore I'm mad."