It’s very common that scammers request pictures you’re uncomfortable with so that they can threaten to send them to everyone they can connect to you unless you give them money. They string you along trying to get you to become attached enough to give them the pictures, then they demand money or they’ll send them to everyone you know. This scam has ended in at least one teen taking his own life that I’ve heard of, and very probably more.
There is no friend who is a 15 yo sophomore, and the person you’ve been communicating with is very likely one or more people working in shifts and also could be men or women. This is their job, or they are being forced to do this, and they are very good at it. They are working on many people at a time so don’t feel bad blocking them. It’s all part of the job for them.
You can do this :)

Yep! If you were to send pics, another possibility is an angry mother or father who will threaten you with police unless you pay them. It’s horrible what they’re doing. <3