Should I Use My Girlfriend’s Shampoo, Conditioner, and Moisturizer? Makeup?

If you’re at her place, and don’t have any of your own toiletries with you, then why not? Your girlfriend has the prettiest hair (we’re assuming) for a reason: she uses great shampoo and conditioner. Ditto her moisturizers, but tread lightly with the stuff in tiny bottles; she’s likely protective of it. Also, read the fine print: you don’t want to walk out of the washroom with glitter on your face. As for the makeup, avoid it. You’re not advanced enough for that stuff. Stay in your lane.