Hmm... I just read about 10 articles on this case and I still see manslaughter (although voluntary, or 1st degree, manslaughter would have been appropriate). The dogs had clearly shown dangerous tendencies in the past and probably should have been destroyed before this happened.
Murder requires intent. 2nd degree murder usually means that you had not planned on killing, but had planned on committing another crime that then led to the killing. For example, if one robs a bank and ends up shooting the guard, that is 2nd degree murder.
Gross negligence is all over this case, but I still haven't seen any intent.
/edit: now one thing that disturbs me is that the dogs had not been destroyed before. Apparently, there was a biting incident a few weeks before the death and, in my experience, a biting dog, especially a large and dangerous dog, should always be immediately destroyed.
Court testimony does not say that that the woman stood by and did nothing during the attack. Now that would be murder. Eyewitness testimony says that she tried to restrain the dog, to no avail.