My friend who lives next door is pressuring me to share my wifi password, but I don't think I should.
Will she split the cost? Why wouldn't you share it with a friend if they split the cost?
No, she doesn't even appreciate it.
Maybe ask her to help pay the bill a little if she is going to use it. You shouldn't have to pay it all if you are sharing it.
She never shares anything with me. That's why I don't want to.
Well it's up to you for sure, and it's understandable that you wouldn't want to share with someone who doesn't share with you. You should let her know you're not planning to share so she can figure something else out.