Once you increase the buying temperature, or do something that she likes or gets her attention, just send her something like this:
Friday, 19:00h, xxx location, apple and cinnamon tea?
Don't give her any room to wiggle out, make her say NO. And it's so hard for them to send No.
Also, with online dating, it is crucual that you #close her the first chance you get. This is a small investment on her part and makes it less likely for her to flake. Firstly ask for a date, and if she is interested in, go for #close.