My daughter has threadworms and we have given her ovex liquid medicine, its been 6 days and the worms havent gone, what could this be a sign of?

Worms ?: I take it you mean the pinworm medicine since there are several products with that name. The PW's are rarely ever seen. The related itching is caused by a body reaction to the sticky film the eggs are lain in at the anus which can persist for weeks. Hydrocortizone cream (OTC) helps this. Many treat PW"s twice, one week apart to kill any missed worms.