Girl suddenly went cold on me -- wondering why?

Met this girl online a couple of months ago. I'm in my mid-30s, and she's in her mid-20s. Things were going well, we met up every weekend, she spent a few nights at my place and we started to share stories, etc. with each other. She used to text me a lot, and we made it a point to stay in touch even during the week, when I'm typically out of town on work. She even added me to her facebook account, commented on a few on my posts, etc. Then, two weeks ago, I shared old pictures from my childhood and she seemed very interested, asked me questions, etc. I had not seen her place yet since she always comes over to mine, and she said maybe next week we can hang out at her place...

Then, the following week, she went on a weekend trip with a few friends and has been very different since she got back. She texted me on her way back asking if I want to catch a movie with her -- I couldn't, because I had to get ready for an early flight and work the next day, so she got a little annoyed (I called her but she didn't pick up and texted me back saying she doesn't feel like talking). We eventually talked and I left for work the next day. Since then, I have texted her, emailed her and called her and she didn't respond to anything. She finally called me after a couple of days and simply said something like "hope your week is going well". Nothing like "call me back" or anything. I called her back the next day, she was at work and said she'll call me during lunch. It's been a couple of days - and no call from her. I think one of the the following is true: 1) she's lost interest, or 2) found another guy, or 3) she's afraid that things were getting too close (like me sharing childhood photos), or 4) she's "testing" to see if I can handle this ... but all this aside, I'm wondering how it could have happened so quickly! Everything was fine until just recently... I'm not going to call her unless I hear from her, but would love your thoughts. by the way, I noticed that she still regularly logs into the dating site. Thanks for your help!
Girl suddenly went cold on me -- wondering why?
Post Opinion