Did she just not receive my text?

So I called her yesterday and asked if we were still on to hangout tonight. She said yes and before when I asked her she said she would love that <3. We do like each other. Today though I texted her Hey. And it got sent as a green text message instead of a blue iMessage cuz we have iPhones. And she didn't respond which is unlike her to do. So I don't know if she got it which I'm sure she did. But also sense it wasn't an iMessage I can't tell if she read it or not. I keep having a feeling she turned off iMessage just so she can ignore my text and end it without me knowing if she read it or not. But that just might be me over thinking. Should I just wait however long for her to text me? I don't want to try again cuz it might annoy her

Oh c'mon! It won't annoy her! Don't worry and try again, maybe she really didn't get your text… Usually girls aren't like that (be annoyed) if you hadn't messed with them.
I'm a girl also!

Well it was just a one-word text, maybe she didn't feel like she needed to respond? Or maybe she was really busy with something and then forgot to respond to it, I've done that. I would definitely wait for her to get back to you without texting her again - Wait until it gets a bit close to hanging out tonight, then shoot her a message saying 'Hey, didn't hear back from you and just wanted to see if we were still on for tonight, or if I should make other plans?' That way it doesn't seem like too much but still gives you an opportunity to see if she'll respond then.

O.k., if this small issue annoys her, pack it in. Surely she will understand. If she turned it off NOT to get your text, obviously she is playing head games… Not good! Instead of wondering about it, I find the best way always is just be upfront, surely she'll appreciate your honesty. There are too many dishonest people out there. Kudos to you, for being honest.
Go for it, text another time and then you'll have your answer!