It is not unusual however, for the subtropics to experience
prolonged warm spells in winter, followed by more cool weather. During those
periods, sometimes crape myrtles will leaf out, and then lose their leaves
again if another frost strikes. Generally this didn't kill my crape myrtles,
but they were in the ground. I guess I would advise keeping th plant which
is leafing out "barely alive" -meaning not watering until the soil is quite
dry on top, keeping it in the very coolest part of the room, as long as
there is sufficient light, etc. In February and March, as the light gets
stronger, you could increase watering, maybe fertilize lightly - and
obviously as the days get warm enough, perhaps as early as mid-April, start
keeping it outside in a very sheltered location.

Well, no need to be concerned about frost while they are indoors. I watered
when I spotted the leaves, and at that time the soil was dry. Maybe I should
move it down to the basement with the others, who so far, at 59 degrees have
not spouted new leaves?