Is her nose still blocked and causing her discomfort?
When my son has flu, he usually can't sleep well either as he is uncomfortable with a blocked nose. What we do is we use a nose aspirator and try to suck out as much mucous as possible before letting him go to bed. In the middle of the night if he wakes up due to a congested nose, we will suck out the mucous again.
If this is the first time your daughter is ill, she could be feeling overwhelmed by discomfort. Give her a bit more time after she recover to adapt back to her normal routine.