It's a backhanded and insulting "compliment". It can easily be seen as if she's saying that she's settling down and he's not her first choice, or that she doesn't see him as physically attractive but wants to have a long term relationship with him because of the "security" he offers. Pretty much almost every man that's attracted to women in some way will see this as a backhanded compliment or negging. No one wants it to be implied or told that they're not sexy or fun.