It possible that, for some reason, she has decided to race down in dosing and when that happens, it can be tough to get numbers to stay over 50. It's not necessarily an indication of her carb-sensitivity. Just that she wants to be on a lower dose. We don't know how much lower. Whether she will settle down at 1U or continue to head lower. I know this doesn't help with your question on how to keep her safe - especially when she is alone at home. If you can get a +1 tomorrow before leaving for work and she zooms up like she did yesterday, you needn't worry. Otherwise, you could load feed her HC from +1 itself. maybe even HC+honey. HC and honey will both wear off in a couple of hours.