I would have loved a few chances to jump ship early. I always prefer when games give you the choice, so staying makes it feel like we did it instead of being mad at the usual (not this one) dumb MC's.
Earliest point, bounce after the BJ if you never engage with another girl.
MC "We are done. Your stuff will be at your parents when you get back"
GF "Why? Are you serious? It was a free pass."
MC "I gave you the free pass. YOU chose to use it. It was a test to see if I was the only one you wanted. I wasn't"
GF "That's sick! Why would you test me!?"
MC *Picture of an engagement ring*
MC "I was going to propose when you got back if you chose me over random dick. YOU chose random dick"
MC *GF Blocked*