Accounts have switched

Hi there,

 

My daughters and I all have Minecrafts accounts. Here is our setup:

 

Daughter 1 plays on Nintendo Switch

Daughter 2 plays on Kindle Fires

I play on a Kindle Fire.

Randomly, daughter 2 was not able to log into my world using her device. I gave her my device and she was able to log in no problem. The weird thing is, she is logged in as herself but somehow gained access to some of the features in my account! She now has 3930 minecraft coins and all of my skins. My account doesn't have the coins or skins anymore. It's as if the two accounts swapped! There is no way she could have hacked it. She and I always play together. Can you please explain how this happened? I'm worried that the security features I have in place have also disappeared.

Thank you,

Christina