She says she misses you so she hasn't lost interest but there may just be less to talk about having not hooked up in real life properly yet. Why the 3 week wait? Have to arrange another date asap and arranging it when she misses you is a perfect opportunity. Personally I wouldn't freeze out a girl I haven't seen in 3 weeks anyway but I also wouldn't text non stop without seeing her in person. Ask her out and be persistent about it and keep being the guy who makes her smile in between. I often mms girls pics of what I'm up to as random interactions. The pic doesn't have to be of you but could be a place, a tasty meal your having at a restaurant, a pic of your new shoes whatever. I have become good at getting girls to send me pics of them too in the process so in between a date I at least get something nice to look at and often something sexy to look at This works especially well with girls who live a fair distance from you.