(This should be in Socialize...)
Well, yeah, your girlfriend is getting upset, because it sounds like she wants to be with you! Part of being in a relationship means devoting your time to her, not all of it of course... but still, the reason she's with you is because she likes you (duh!) and wants to spend some private time with you. Not "shared" time like, "Oh, come with me while I train! Watch me do this kong over the table!" It's okay to spend
some time like that, but no girlfriend is just going to sit and watch you practice all day.... Likewise, would you want to spend all your time with her following her around as she shops, or do nothing but watch her favorite TV show?
If you and her are going to continue together, I think you should take the time to say "I want to train on these days, or at this time, and I want to spend this other time with you, doing things you (or us) want to do."
Be flexible. If you think she's sensitive about how little she sees you, and you truly like her, then show her you like her and spend more time with her! Even if that means cutting practice short, or spending one less day training. Really, that much time is
not going to affect your training, but it will
definitely affect your relationship. Show her how much you like her, treat her to something she likes, give her a nice massage, tell her about all the things you love about her, pamper her, etc. Girls like it when you treat them nice, and don't be afraid to be creative and romantic.
[This is all assuming that she does not have any separation or dependency issues. If this is your / her first relationship, then realize you / her may not have matured emotionally enough to work things out... which, even though it sounds bad, is still okay. Everyone grows up, just like everyone was once a newbie

.]
My 2 cents

PS: I probably wouldn't keep asking her why she doesn't like you practicing... otherwise, you're kinda putting her on the spot, and you're gunna have a bad time.... Really try spending more time with her first.