How to make Messenger forget a previously used Messenger contact?

I installed the Messenger app on my wife's phone and have been communicating with her via my inReach Mini 2 from the Messenger app on my phone. However, she said she would prefer to communicate via regular text on her phone. I deleted the app from her phone, deleted her from my contacts in my messenger app, and all of our message threads. But when I try to compose a new message, as soon as I type in her phone number it comes up as a messenger contact, (the two little white dialogue boxes on a red background beside her avatar), instead of a phone contact, (the white handset symbol on a black background beside the avatar). I have even tried turning off access to contacts in my phone, but it still remembers her phone number. How can I make my messenger app forget her phone number, so I can start fresh texting her directly to her phone?