I honestly think this kind of thing would happen 90% less if guys just stop texting.
There's no mystery, no excitement. She can contact you whenever she wants and knows you'll reply and be available at her leisure. It's weak. You have to live your life and she has to want to be a part of it. Even if your life isn't the most interesting one, she'll THINK it is the less she knows about it. Learn to hype yourself.
So what if a girl texts you? Well here's what I do. Whatever she says, you can just give a short response and say "Kinda busy now, I'll call you tomorrow some time" or "Haha yeah, anyway I'll call you soon". Purposefully condition her to not text you as much. Oh, she'll want to, but she know she can't text you too much after you cut her off a few times like this or she'll come off as too needy and you'll lose interest. Now you're the guy she wants to text, but is afraid too and just has to wait for his call. In the mean time the others guys she's texting just become so easy and unchallenging. You stand out.
She'll automatically assume you're doing something more engaging than texting with her. Maybe even hanging out with another chick, even if you're just sitting on your ass doing nothing. Then you're free to call her whenever you want and she doesn't know when, you're making her follow you and your schedule and doing it so beautifully subtlety she won't have a chance.
When you call it's for a few minutes and you always end up asking her out again. Attraction happens IN PERSON and technology should only be used to facilitate meeting in person. This is why long distance relationships almost never work.
I'll give you an example from my life from a long time ago. There was a girl who I had been seeing, keeping with my all my rules and we went on some dates. One day we made out and the next day she freaked and called (notice how she's already conditioned to call me instead of text?) to say she couldn't see me anymore (she was religious). I called her on the phone and we talked about it and she agreed to come to dinner with me. Then she cancels by text. I don't reply, but call her the next day. She doesn't pick up. I text her "Hey, if I call you, are you gonna pick up". She replies "Sorry, call me in an hour". I call her, tell her it's okay and I understand. Then I let it lie for a couple of days and call her again and manage to set up a date (btw, a good line is "Hey, don't take this the wrong way, I dont wan't you to freak out again, but I want to see you again"). We finally meet up and every goes well and continues as it was.
See, how I worked it there? I only used text to set up a phonecall. Used a phone call for pleasant conversation and charming, but mostly to set up a meeting. I would never have gotten her to see me again only by texting her. There was way too much resistance (cause of her religion). I probably would have only reinforced her decision.
Right now, your girl has lost interest. There's most like another guy. The only thing you can do is NC. Let her wonder about you and contact YOU. Then implement this. Your only text reply to her should be "Hey, kinda busy now, I'll call you later". Then call her later. In the mean time, don't just sit around. Go out and meet some more girls! You'll come off as less desperate and needy with other girls in your life. Unless you're a really good actor and can manage without that. Nothing wrong with faking it til you make it, but it being genuine is always better.