If a child age 5 has a low grade fever on monday and on wednesday she gets a shower, how long do you need to wait before she goes out after said shower?

No waiting. It is a myth that sick/feverish people shouldn't bathe. There are no reasons to limit bathing/showers during or after fever. In fact, many people like a warm bath or shower to ease their discomfort and the humidity relieves congestion. Once your child is dried off and dressed, he/she can go outdoors.
5 to 10 minutes. She may go out after the shower as soon as she has dried off well, dried her hair and dressed appropriately for your weather conditions.
NOt set time. There isn't any set time/guideline for this...Just use your common sense. If she has no fever now, do the usual. If she still has fever, then treat it; make sure to dress her warm, use caution. If she appears ill, get her to the doc...