Never text because you’re bored, or because you want a reaction. Text her only because you have something to say that she wants to hear!
I’ve also noticed that more attractive and more successful women are worse about texting back than less attractive women. Many of the most attractive women I’ve ever dated were women who didn’t respond to my first two texts, but who finally replied when I sent text number three.
To summarize – you want to send at least three texts, on three different occasions, before you presume she’s flaking on you.