When a girl ends with "text me later", should you really text her?

A girl I've been on two dates with, planned a third date with me and she's always very enthusiastic over text. I only text her to plan definite dates while we're getting to know each other. After the second date we ended up texting the next day to plan the third, all the while she was shopping and telling me all about it, and being all flirty with me, etc. Finally I said I would be studying and going to bed so I wished her a goodnight and a good weekend, to which she enthusiastically replied with a long message, ending with "good luck studying! Goodnight :) text me later!" I wasn't sure what she meant with text me later since I was gonna sleep soon, but I figured she meant sometime within the next day or two. Books I've read about dating women have all said to not do so because it makes you look needy and like you have nothing else going on. I'm a very busy person so naturally I haven't texted her and it's been four days since. Is this boosting her attraction level by providing mystery or am I being a douche? lol