What to say to someone who feels guilty about mourning someone's death?

Okay so I know this girl, and her mom was murdered about two years ago. And she never really got over it. She cried at the funeral, but after that, she pretended like it never happened. She's had a really bad relationship with her father for almost her whole life, but after her mom died she moved out (she was only 15). She worked to pay for her own place and refused to stay with anyone else. So now she's 17, and her father just died and old wounds are being reopened. She told me that she feels guilty about being so upset when she didn't even have such an awesome relationship with him. She said and I quote, "I feel so bad about being all upset when so many other people go through SO MUCH worse. How can I sit here feeling sorry for myself when I'm so well off compared to others?" But it's not just her fathers death that's making her upset. I can tell. She feels guilty about where things went (even though he really was downright horrible he was really nice sometimes) with her dad, she's still upset about her mom, and her life is basically crap. She also likes someone but won't go near him cause she's afraid of getting hurt. So instead she pretends she hates him. But her feelings are getting SO in the way of her life and she's too scared to address them. Then only people she talks to - when she talks about her issues at all - are me and our other best friend. She holds in her issues and pretends to be happy but we can tell she's not. And when I try to talk to her, she makes some excuse about being tired or having to study or she completely denies everything and says she's fine. So now she's stuck in this rut where she likes this guy (and he likes her too) but she won't go out with him cause she's afraid of getting hurt (she's had horrible experiences with men in her life, btw) and she won't address her feelings all because she feels guilty about being upset when (as she puts it) there are lots of people that are far worse off than her, so why should she be? So what do I say to that? She is absolutely right about people being worse off than her, but that doesn't mean she can't be upset. So how do I tell her this? How do I make it okay?