Do you think I should be wary of this pen pal?

No, it's not possible for two people to have the exact same email address. I think that's very suspicious. Ask her about it if you want. While I think it's unlikely, there is a chance that there's a perfectly logical explanation for this. Like I said though, it's not likely and I don't know if I'd even trust the explanation she gives. Really, I think it might be best to just end this penpalship. Don't give out your home address at first to anyone--I think it's far better to invest in a PO box because snail mail pen pals are generally better than epals, but you have to keep yourself safe and getting a PO box helps you do this. Certainly don't give any address to this person, even if you do decide to continue your penpalship. I hope this helps. Take care! :)