Why are we not together?

There is this woman that has come in as a trainee teacher in the school where I work. She is 25 years old and she is single. We talked and exchanged numbers and I tried to go out on dates with her but she says she doesnt have the time due to her studying for a teaching degree and she also owns her own business by selling food in the afternoons some days for a week. To tell the truth it is also difficult for me to go on dates because I am saving to get a car. Anyhow, I never admitted to liking her or showing any real affection but she said she knew I liked her and she saw how I always sneak peaks at her when she passes. She told me this on Facebook. One afternoon when I was talking to her, on Facebook I told her she looked really hot today wearing that tight black skirt. She laughed; told me jokingly that I should be paying attention to my class and then she told me to go on Whatsapp since I have an account there too. To my surprise and great pleasure, she sent me a nude front photo of herself! She of course told me to delete it but I saved it to private photos on my smartphone. I will never, ever show anyone else those photos and I don’t plan on doing so because I like her and I respect her privacy and trust. The part that is confusing is that I tried to get her on some dates after but she always never goes because of excuses dealing with her studies and work. Once we hung out together but that was a staff outing so it wasnt really personal. Just recently we chatted again on Whatsapp and she send me some nudes; after I begged (like I said, she does not do it often very rarely and on occasion). My question is does she really like me? If so why doesn’t she make time to go out with me? My friend noticed the way she talks to me and he says it is because I should be more assertive, maybe that is true but we do work together and I do not want to make a scene at work so I ask her on dates discreetly. Bottom line, I do not believe that it is just circumstance that she is blowing me off.