iMessage

Hello Cap_88,

Thanks for using Apple Support Communities, it's great to have you here.

We have a couple ideas as to what may be going on here that we'd like to share. The first thing we recommend is checking your friends contact card in the Contacts app on your iPhone. Check to see if you have her listed with her phone number or her Apple ID (or possibly both). It's possible that you are sending messages to her phone number and that she is only using iMessage with her Apple ID email address. If that is the case, then she could have iMessage enabled but your messages would still go through as green bubbles (SMS). To resolve that, you can check your thread with her in Messages and make sure you're messaging her Apple ID email address instead of her phone number.

The second thing to check is that you have your phone number and Apple ID email address both set up in iMessage as expected. This article will help with that: Add or remove your phone number in Messages or FaceTime - Apple Support. You can also share this with your friend so that she can double check that she has all of her contact info set up in iMessage as well.

We hope this information is helpful!

Have a great day.

Do both of you have Internet connections when you're trying to send iMessages to each other?

Although SMS messages are sometimes used to set up iMessage, iMessages travel mostly over the Internet. If a phone does not have an Internet connection (e.g., because you normally keep cellular data turned off, and you're also not connected to a Wi-Fi hot spot), iMessages sends will time out and you'll eventually see "Not delivered." Then you might get options to retry, or to send the message as a SMS/MMS message.