Am I just a friend?

Hi everyone,
I want to ask you for some advice since I don't really know what's going on.

The story begins like this, approx. 2 months ago a customer came to the company I work for. I gave her my personal number so she could contact me directly. I use to do this with most of my customers, this way I know when to schedule the meetings and for how long even when I'm away. At that moment I was in a relationship so I didn't care that she was, let's say gazing at me(but not sure).

Couple of weeks later she started to send me messages telling me things from her personal life. We had talked before using messages, but only simple conversations such as "Could you come at XX:XX PM" or "Call me if you need any advice", things that I usually talk to my customers. I answered her messages with very short answers ("ok" "it happens..." "I know...") because back then I was in a relationship but I tried to be polite to her too. She even called me once for about one hour(she called me just to tell me what she was doing... ). One day she sent me like 30 messages in 5 minutes and I told her something that she didn't like because she was getting annoying. She called me an asshole and she said she doesn't want to hear anymore of me...until the next day when she texted me that she is sorry and apologized. One day she came to where I work and she was laughing without any reason and she said she felt great... I am not sure what reason she had, because she had come with some issues.

Shortly after, she started calling me every Sunday/Friday. Since last Sunday she's been calling me every day for 2-3 hours at least. I've never called her or started a message conversation with her, she only did that. I haven't called her not even once, except when I found a missed call from her.
From what I've talked to her she made me understand that she's only talking much to me and her mother and that she usually avoids many people. She is a student and she study at a university in another city, but she's from a small town near my city. She's always telling me that her roommates keep teasing her "who are you talking to, who's your boyfriend,...". I have to mention that she is a bit childish.

I would like to get in a relationship with her since she is a great girl, but I have some doubts about that.

What makes me think something is not right:
- she's telling me too much about her family
- she's telling me too many details about her roommates (who she hates, who she likes, why), things that you usually talk to friends not bf. but maybe I'm wrong.
- she told me that she calls me because she knows I want to talk and listen to her. This, in my opinion is something weird.
- she's been talking too much about her problems. This sometimes gets very annoying.
- she's not too curious about my past, although she told me a lot about hers. She asked questions about me, but still...
- she is talking about facebook but she hasn't added me as friend. From my previous relationships I know that adding friends on facebook is pretty much a first step.

May I ask what your opinion is ?
I'm sorry for the grammar but English is not my native language.