Alexa connects?

I hope someone can help me. Brand new, my sister and I have each received and furnished an Alexa. (She does not live in the same household) During setup, we noticed that we can access both Alexas, or even "remove them from the household". I did that because I had your Alexa on my app. Now you can no longer access your own. How can that be? Why are the two Alexas so connected? We do not share the same Wlan network, same household, or Amazon account. We just ordered the Amazon Fire tablet years ago, where I was occasionally online with your Prime Account. But I never logged in to my phone (Huawei).
Is there a way to remove this connection without having to re-access your Alexa and re-setup everything? She also has my Amazon Echo in her app!

Alexa is connected to the Amazon account. If you both use the same, they hang together no matter where they are physically.

That makes sense, but we do not use the same thing.

Were the Alexas bought separately or together by a person with an account?

I know that from FireTV, that's always set to the buyer's account.

I would both times completely reset and remove from all accounts.

Neither. My alexa was even bought in the store, so that's all so confusing. "

Then check with which account the respective Alexa is registered. Mutual influence can't take place if there are separate accounts

It is still a mystery to us how this could happen. Have you removed in my alexa app (was as a household inside) then your alexa was back to 0 and now we're no longer connected! The reset has worked so!