How to remove Apple Account in an iPhone?

Hi! Long story short, I purchased an iPhone 15 from a friend. Unfortunately, when the phone was delivered to me, she forgot to remove her Apple Account and she instructed me to just sign her account out. However, all the passwords she had given me didn't work and she said that she might have forgotten about it. I did the following already to reset the account's password but to no avail:

1. Reset the password using my iPad in the iforgot apple website. Still waiting for Apple's response.

2. The phone's activation lock is turned on so I had to request to Apple using my friend's receipt purchase but somehow, Apple still denied my activation unlock request after providing the necessary documents.

Now, I can't reset and erase all contents of the iPhone 15 in settings because it requires me to turn off the activation lock which I can't because I don't know the password of the Apple account. What should I do? Is there an alternative way to reset this phone? I have already tried through iTunes using my phone but whenever I connect it to my laptop and press "Trust this computer" on the iPhone, it requires Face ID too which would not work because my friend is living overseas. Please help me out! Thank you in advance!