Is this Metro PCS thing a scam?

Ok so on this app, called Mercari (where you can sell electronics and a lot of other stuff, it's safe), a transaction went with no problems. She got her iPhone 4, I got my $85.
*I reset the iPhone 4 to its original factory settings and basically wiped out every single thing that was originally on there. I took out the SIM card too. Since I wiped out everything, I believe it is unlocked.

Now she is saying that the iPhone 4 is still locked and that she has to pay $60 to unlock it. My dad thinks it's a scam to get some money back. (She paid $85 plus shipping). She has zero ratings on the app too, which makes the whole thing even more sketchy.

Is this a scam? Or does Metro PCS actually charge $60 to unlock it? Any help would be greatly appreciated. Picture of our conversation is included. Is this Metro PCS thing a scam - 1

You are wrong in believing that wiping everything out will unlock a phone.

Is it unlocked from your iCloud account? If not you need to log into your iCloud account and remove that phone from your Apple ID and iCloud account.

If this was NOT a Metro PCS phone originally it needs to be UNLOCKED from the carrier it is locked to, so that she can activate it on Metro PCS or the carrier of her choice. Have her take a picture of the IMEI on the back of the phone, to make sure that it matches any paperwork you have from the phone that you sent her. Then have her ship it back to her and when you get it, send her a money order for the two way shipping and the cost of the phone.

You and your Dad, not understanding or knowing what unlocked means, when it comes to a cell phone, is NOT her fault or problem, that is all on you to make it right. So if this was a Metro PCS phone, you call them to find out what they charge or if the charge to unlock phones originally sold through them. If this phone was an AT&T or T-Mobile phone, you will need to get the unlock from them, if you are still a current customer of theirs.
A carrier will only unlock a phone that was bought through them. An unlocking service is the one that will be charging her to unlock the iPhone.

A buyer does NOT need to have any ratings on the service, the SELLER on the other hand is the one that will be looked at as sketchy, saying that they didn't know they phone was not unlocked. So that sketchiness is YOU not the BUYER.

If it were me as a the seller, I would have her send the phone back and refund all her money, including shipping (both ways) for YOUR mistake.

Yes you have to pay to unlock a phone., that's normal. Doing a factory reset doesn't unlock it with the company you had an account with. You need to call the company you had an account with and tell them to unlock the phone. But Metro PCS might also have their own fees to activate it
Call Metro PCS in their 800-numbers say you bought a used phone and ask of they charge a fee and how much it is

It doesn't comes pre-unlocked, you need to unlock it first and you must also have one app that can make your mobile totally secure and that is Leo Privacy Guard.