I think you'll find that either publishing an ARP entry or filtering incoming packets in the kernel is required for handling a TCP stream over raw sockets.

As the outbound TCP SYN is manually crafted and sent over a raw socket, without any corresponding state table entry on the sender's kernel, incoming TCP responses will be rejected by the kernel with a RST.

I suggested to Julia that she manually publish an ARP entry for another IP which she could send and receive on. The kernel not having an interface with that IP assigned to it would ignore responses while also passing them to the raw socket. An alternative would be to use an iptables rule to drop incoming packets for the relevant flow - although that may be more difficult to manage depending on what you're doing.