If you've nursed a terminal Ebola patient 99.5 may indeed not technically be a fever, but it's something you should pay attention to. Heck, more to the point, she should know her normal temperature range at the various times in the day and if that's a fever for her. In the morning it would be a fever for me, I run a bit cool.

Also note even the professional WelchAllyn units are not 100% accurate, they're rated for 0.2 F plus or minus (I bought one not long ago after my old el-cheapo BD one died and Amazon reviews revealed today's el-cheapo ones are by and large worthless. Heck, 3M even created a new consumer brand, no doubt to avoid brand damage to BD).