My message won't send as an iMessage?

So my friend just got an iPhone today. I've had one for a while. My phone refuses to send my messages to her as an iMessage. For anyone else that has an iphone, my messages send to them as an iMessage, except her. When she sends me messages, the come in as an iMessage, but mine send back as a text message. We both have iphone 5ses. I have tried everything. I have changed her phone in my contacts as an iPhone. I've tried deleting her messages, and even deleting her contact and put it back in. What can I do?

Becuse it's an iphone.

Go to settings and make sure that iMessage is switched on. I had this issue recently.

If she has her data turned off and isn't connected to Wi-Fi then iMessage won't work. It also won't work if she has gone into her settings, disabled data usage for iMessage and is not connected to Wi-Fi.

Btw does it really matter? Almost every plan has unlimited texting if it's got data.

She has to turn on iMessage and use iCloud settings on her phone or it won't. You said she just got it. She hasn't set it up completely yet. Best luck.