I love both Tonks and Remus, but they are really flawed humans. I understand that we are not the same, and Tonks had a very different personality from mine, but you don't rush off to a deadly battle after your husband, when you have a few weeks old baby home. You just don't do it, even if you are an auror, even if you adore your husband. That baby needs his momma, and you will be an easy target during postpartum period, so it's just plain stupidty to go. But she was young, in love with Remus, all of her friends were fighting, she was a member of the order, and an auror. And she was well... who she was. There was no way she would have stayed home. Poor Andromeda.