My friend is only 22. is it normal for her to get.herpes zoster in that age?

Can happen any time: Herpes zoster can happen to anone who's ever had chicken pox. Most of us have had chicken pox, thus most of us can get zoster. Zoster at younger ages typically can be brought on by stress or other insults to the immune system. Maybe your friend is under a lot of stress? Not sleeping enough? Have her see a doctor, she can and should be treated for her zoster.

Unlikely not abnorma: Herpes zoster is reactivation of chickenpox which is a typically a childhood disease. However, we now have the ability to vaccinate against it (if your parents allow!). But once you've recovered from chickenpox, the virus goes into hiding until your immune system is low enough to allow it to spring back as zoster. However, this typically happens in the elderly. So we need to confirm diagnosis.