My daughter has developed a hive-type rash that
starts on her ankles late in the evening. the
rash itches, her skin is red and feels hot and
burns. The rash at this point seems to come and
go, but mostly seems to show up in the evening.

Do they salt the roads where you live? She could be getting road salt on her during the day that could be irritating her skin....
Did you recently change laundry soap? Residue from a new soap on her socks is another possibility.....or it could be just the cold and damp....ankles are very vulnerable to that sort of thing, especially when you come in from the cold and your damp socks start warming up....
Try having her put on fresh dry socks when she gets home.