Wife has access to all my messages from five years ago

suddenly my wife got access to all my texts from 2019 and before on her device as if she was the one texting them. I don’t know how, I never logged into her device on iCloud or anything.

We don’t have a shared iCloud account. We have separate, distinct numbers, her device is not registered under my iCloud name, nor was it ever my device (e.g., not my old phone). We don’t have a shared MacBook or IPad which could sync anything.

I changed my iCloud password but it seems the texts are stored locally on her phone.

I don't, and have never had message forwarding.

She received a message from a mutual friend which included text history that she recognized did not sound like her, and realized it was all my messages but they appeared blue on her phone as if she was the one sending them.

I’m at a loss at how this could happen. My only guess is that I sent her a couple contact cards recently and somehow that triggered this back door bug?