I'll help you out. As Cthulhu, I've been watching you guys since you first appeared and started doing your stupid things.
Girls want a man who can provide for them, so here's what you do. Head out to the prairie, Kansas or Nebraska will work, and find the biggest buffalo around. Kill it with your bare hands. Now, the native Americans used every part of a buffalo except the grasnizoot, but unless she had really high standards, you won't have to use every part.
Make its hide into a fur coat. Cook its meat into a delicious dinner. Inflate its bladder to use as a friendly dodgeball for when you're goofing around with her. Make its bones into jewelry, and bury its skull near an anthill. After a few months, dig it up and it'll be picked clean. Cut out the bottom of the skull.
Give her all of the things you made with the buffalo except the skull, and she will love you, because she'll know you'll never let her be in want.
The other side to girlfriending is keeping her. This is where the skull comes in. Wear that thing. If you've got extra bits of leather from the coat, use them to cobble together a loincloth and maybe a shoulderguard. Tattoo a demon face onto your chest. Maybe kill another buffalo and put its skull on the end of a staff(But be sure to put some feathers on there too). No one will ever hit on her when you're around. Ever. That's how I kept my first girlfriend.