Not receiving texts from iphone

[bbbss]

I have a Verizon Note 3 and I used to be able to receive texts from my friend who has an iphone. However, since she got a new iphone, I cannot text her or receive texts from her. Group texting in general with iphone users is sketchy- sometimes I get them, sometimes not. What is going on?

 

[SpookDroid]

Was your number ever registered on an iPhone? When your friend tries to message you, are the 'bubbles' in her phone green? If they're blue, her phone is recognizing your number as an iPhone and is trying to send you iMessages, not SMS/MMS.