Decayed messages to a certain person.

I have an iPhone xr, and my mom has the same xr as well. When I text her my messages won’t send to her till several minutes later. Almost hours later. I’ve noticed that the delayed messages is only when I’m texting her. My friend has an iPhone 9 and I can send and receive messages with her with no problem. My mom has also noted a delay in her messaging me. Is there something wrong with our phone specifically?