should i be concerned?

I have been seeing this woman for a few weeks now , and for the first week everything was great, we spent all our time either together or texting or talking on the phone. However here lately we have been getting into some really deep discussions we both agree on or talking about sex or something I promise and she replies she will hold me to it and when i tell her i want to prove its more than words she replies with, shes guarded and will let me in time that trust is a big thing for her , or she just poofs and i hear nothing for hours. Some of the conversations she has brought up with explicit detail, things you dont say if you don't trust the person but yet still says shes guarded. This is frusterating and confusing at the same time. I dont want to over analyze or anything like that. I have spoken to the friends that hooked us up and they say her ex put her through a lot of crap. So i'm wondering why she would open up like that and suddenly withdraw and say its because shes guarded. Yet she talks about how she loves I’m not pushy and that we compliment each other so well and that im family oriented and an open person. This time its going on 5 hours where i have sent a few messages and get notified when she reas them but she has not replied. No saying she had to go or that anything was wrong or anything. One min deep meaningful convo the next no word at all.