Imessage typing bubble indicator not showing up

Hey i recently got a new phone from my old IPhone 4 that had IOS 7. I now have an IPhone 5S with IOS 8. When i used to text my girlfriend with my old phone she would always see the typing notification bubble telling her that i'm typing a message...now since i upgraded my phone she doesn't see the bubble on her end anymore. She is still using IOS 6 on a IPhone 4S. The typing bubble shows up on my phone when she is typing something but she hasn't seen it since i upgraded my phone.

I was wondering is it because she is using IOS 6?