I'm going to refuse to walk my girlfriend home alone
Are you serious? Why wouldn't you walk her home?
My friend can do it instead of me.
Just because you do not feel like doing it, does not mean you shouldn't do it. It is your obligation to walk your partner home when she asks you.
I just don't want to. My friend is willing to do it, so why can't he.
I guess it's good that someone is doing it, but you should really be the one to help out your girlfriend when she needs it.