Have you taken her to the dr? Do you think she might have an infection and need an anti-b? Caitlin's (touch wood) not really had a temp before so im not much use...
Caitlin usually sleeps in the same as sophia. Does your heating come on in night for long? Id be worried about her getting too cold if you lost the vest.... But then I know you dont want her burning up.
Could you maybe put her down in vest and babygro and blankets, that way if she feels too warm take a layer or two off or add another if she feels chilly? Svae faffing about trying to get sleeping bag off and disturbing her.