First of all, welcome to the forums!Had the s4 for like 6 months now and I randomly can't get MMS from my girlfriend who had an HTC one. It was all random I can send her them and she gets them. I tried the settings WiFi on off etc. Its getting a bit irritating now.
Thank you.
And thisDid you Mark her as spam by accident? Go to your messaging app and press the menu button, then press spam messages. Check if her messages are there.