DO NOT ask her out or show any signs of wanting to ask her out. You have already showed your interest and she declined. If her interest has risen she will ask you out.
I totally agree with the AMS video above ^^^. You just keep taking your sweet old time responding back when she reaches out and do not do anything that shows indication of interest. She will eventually crack and bring it up and then at that point its a one shot deal for her to come over to your place for a drink. No date.
A few weeks ago I had a chick flake on me that I assumed had extremely high interest. She reached out first through social media (DM) and after a few messages I set a date. She was doing all of the initiating until the day of the date and totally disappeared. No big deal, I went silent.
After a week she sends me a "hey". I just said "hey whats up.....I am busy and I cant chat right now". So she says "sorry, message me when you're free". I tell her no problem and then I DID NOT message her later.
Later that night she sends "I just wanted you to know that I am really sorry for disappearing, blah blah blah, but I still want to meet up".
Me: Ok cool. Things are pretty busy right now but I could sneak you in for a drink at my place on Sunday night.
Her: Well I dont normally come to someone's house on a first date. I was thinking we could go out for drinks.
Me: Well our first date was last Wednesday and you disappeared so that was the first date. If you dont want to come over Sunday night we can try again later on when the holidays are over and I get more free time. Hit me up in a few weeks.
Her: What time were you thinking Sunday night?
Now keep in mind that I have physically met this chick while out with mutual friends a couple of times so she was not just a total stranger. She ended up coming over. I am still making her do 90% of the pursuing and initiating (text, etc).
When a chick does make it easy to get together you should pull back IMMEDIATELY and simply tell her "No problem, maybe we can try again later on". Then go silent.
If you continue to pursue her, it will drop any interest she does have down to nothing.
If you walk away, it could raise her interest and its the only shot you have of her coming back around. If she doesnt, you wasted no time on her after she failed to make getting together easy.