<human>: Can you give me a shortened version of the text?

Hi Reddit!

I have been dating my wonderful girlfriend for 6 months. She and I are compatible in many ways, but she has had a fairly stressful/traumatic life (parents are both alcoholics, was possibly molested as a child, has been in 2 abusive relationships, and was sexually assaulted while abroad, among other things) that sometimes cause what I perceive to be communication issues.

In my past relationships, I have not had any issues with clear communication. However, my current girlfriend will often tell me about difficult situations, upsetting thoughts, triggered emotions, etc. related to her past, followed quickly by "I don't want to talk about it". Just the other day, I could tell that she was upset after she had visited with her parents. When I asked her about it, she refused to tell me why that visit was upsetting. 

While I understand that different people have different boundaries, and that she is entitled to her privacy and only "obligated" to share whatever she is comfortable divulging to me, I find myself in a unique position. I find it oddly unsettling when she refuses to tell me what is going on with her, particularly because her past continues to exert a fairly strong influence on her present mood and outlook on things. However, I also understand that she's probably scared to be completely forthcoming with me about some of her more difficult experiences, both because doing so would make her feel vulnerable, and because that requires A LOT of trust. That being said, the privacy has made it difficult for me to feel like our relationship is progressing, and has made it more difficult for ME to build trust in her, given that there are so many things that I'm not "allowed" to know about. 

Does anybody else have experience with this type of situation? I love my girlfriend and am committed to her, but I'm not completely satisfied with the level of communication we have at the moment.
<bot>: girlfriend has had a traumatic past that continues to affect her today, but refuses to talk to me about it. I find this frustrating, but I also understand her reservations. Help!?