She may have stopped sending you flirtatious texts because she feels that she has given you more than enough indication that she likes you.
Hence, she may feel that she would come off as desperate if she were to just keep on initiating flirtatious texts to you.
Even if she may know that you like her, she would still want you to make the ultimate move in asking her out.
This may be what she is waiting for now.
You should ask her out as soon as you can.