I have had the same. They give me all signs to ask her out even give examples of what we could do, when I do ask them out they flake or give excuses. Then I go ghost for a period and they text or call again. Maybe shes not comfortable yet or they feel like they could have you so its enough for them understand? They feel like wow thats easy he already asked me out, hmm i look fat in this dress, or I dont feel like going out, is this going to fast? Their hamsters spin crazy and they could flake or see what your gonna do when they flake.
Just lay back easy tell them its ok and put her on the backburner, most of the times she will ask you out in a week or so coz her hamster spins if your still interested.
Also its a numbers game like GoTed HIHGLY intersted women WONT flake, period.
Mostly shes interested but not interested enough to go out with you alone so shes still making up her mind and since you asked her out she knows you are interested so her ego is stroked thats enough for her, what you should do is be indifferent and polite so she feels that she can loose you and she will come back to you
