Can't text or call one specific contact but they can contact me

I have an iPhone X and this problem just started in the past 2 weeks. When I try to reply to texts from my mother in law, the text box is green and they don't deliver. When I call her, it goes straight to voicemail. She can text me and I can see them, just can't successfully send a reply. She is not blocked, nor am I. I have rebooted both our phones, deleted her contact, reset network settings, toggled airplane mode, and turned on and off iMessaging. 

I have had no changes to my phone besides the software update, but this problem was not there a few days after the update. My mother in law also has an iPhone X

Please help me! Apple said they have never heard of this problem