Hello,
Welcome to Healthcaremagic.
From your I understood that you have misused
Diphenhydramine gel caps.
Diphenhydramine gel caps are made for systemic use.
Usually people misuse Diphenhydramine itch stopping Gel by taking orally. But it is to be applied topically.
Probably it may not cause overdose, as you used for topical purpose.
Overdose also depends on age, weight, Health condition etc..
Usual overdose symptom of Diphenhydramine is
Drowsiness, Confusion, Agitation, Low
fever, stomach pain and
rapid heart rate.
Some serious side effects are also reported like Seizures, Coma and
delirium.
If your friend have any of the above serious side effects, move her to ER.
Hope this helps.
If any doubt, Kindly reply.
Take care.