My girlfreind seems to have trouble showing her feelings ,is it normal ?

My gf and I have only been seeing each other a few mths and that's broken up a lot to bc she's 21/2 hrs away.We also got of to a very slow and cautious start bc she's been hurt a lot.

From day one she's gone to all sorts of lengths though for us to be together , she also talks about me a lot - nicely , and she always seems to love our time together but !
She doesn't actually say anything much nice to me , she actually jokes around a lot and calls me stuff instead as we both do actually that's sort how we got together in the first place , nother story. But she won't say anything nice in seriousness or admit to missing me or loving me , even though she's here in a flash when we can and usually looks really exited to see me and that stays with us , we have heaps of fun. Or if we are together and I've had to leave for some or we've had a fight , people have told me she's never the same when I'm not there.
Yet she never says anything nice, won't admit to anything. Won't even admit to missing me , or thinking about me a lot. Or when I stur her about how much she's gonna miss me or really feels , I've taken to sturing her about- new tactic , but more jokes back or messing around names and then a nahhh , bullshit.
She's never wavered though around me or about us , it's grown , heaps , but still nothing.
Is she scared to show it , is this normal for someone that's been hurt so much and that has been rough believe me, won't go into it though but anyway . Will she give in once she knows she can trust me , is she testing me before she does - what's going on with her?