Me and my gf have been dating for couple years and living together for half a year now. We get along really well and haven't had big problems. If we did, we have survived everything well. However there's this problem where we strongly disagree: 

Because I'm living in a permanent apartment and she moved from far away with little belongings, I have been generous and we have shared everything we have. Sometimes though I've been little annoyed, for example when she eats snacks I bought and reserved for myself without asking me, or if she just grabs my phone to play with it (even though there's nothing I want to hide from her). 

Last Christmas my family bought me a small bottle of fancy shampoo. My gf has a big bottle of shampoo for women. She has a long hair so she uses quite a lot of it. So when I started using the new shampoo my gf just casually asked before going to shower if she could use it. I thought for a while and said no. Maybe I was tired of sharing everything and wanted to have something, even small, of my own. Besides my family got it as a present for me, and I was afraid my gf would use 1/3 of the small bottle on her hair.

She got angry and stormed out of the room. She spend the next hour sulking locked in a room and when I tried to ask why she's mad she just said she feels uncomfortable if there's something I don't want to share with her and she doesn't want to talk with me.

Should I just share literally everything, even gifts for me, with my gf or is it normal to want to have some personal items of your own in a relationship?

TL;DR: Didn't share my gift-shampoo with my gf because I want to have something of my own, she got mad and will be uncomfortable if I don't share everything.