How does someone remotely delete your text conversations that are on your phone?

I was talking to my best friend about an embarrassing moment of hers, when I went to reply the whole conversation -- in our whole life-- has been erased.

I called her and asked, "Hey! Did you by chance delete our text conversation?"

She said, "Yeah! I didn't want anyone reading that!"

I said "It deleted the whole conversation for me as well!! How did you do that? "

So then I sent her some messages, deleted the conversation on my end, and it didn't delete her text conversations on her phone. Only mine.

So then she sent me some messages, and I sent some back and she deleted the conversation again, and they disappeared on MY phone. But when I do it, she still see's the messages and the conversation.

What is going on!? Is this a new feature? I have the iPhone 12 Pro max, and updated the software to 15-- version.

If I want to recall our text conversations, how do I do that? But honestly, I want to know why she could delete our entire text conversation on MY phone. I feel like that shouldn't be able to be done, and some how it did! But it didn't work for me when I deleted our text conversation, she still had access to our text conversations.

This is bugging me!! I feel a bit violated-- a bit dramatic-- but someone being able to do something on my phone, is NOT something that I want!! Luckily it was her that did it, and its fine, but if it was a text message I needed to keep or have, or wanted to keep, and it was just deleted like that, I want to know -- is this now doable??

HELP!!!

Also more info:

we have different Apple ID's

She has an iPhone 11 and I have the iPhone 12

She did it when she was 3 hours away from my house, so we weren't even near each other.

I didn't do it, by accident either, because I was hardly on my phone all day! Barley noticed that she wasn't on the top of my text message feeds, and when I clicked new message, and texted her, it came up as it was the first text to her. Then I asked her and she told me she deleted it on her end!!

This is so crazy! Thanks for the help!

Catherine.