What is the correct way of using Spotify on Amazon Echo?

Ich connected my (premium) spotify account to my Echo, which works quite good as long as I'm at home. But everytime I'm on the road listening to Spotify via Android-App and bluetooth and my girlfriend starts spotify on my Echo at home, my phone stops playing. If I press play again, the echo stops playing the song, my girlfriend listened to on the echo. That's pretty annoying. Do I really need a third account just for my Echo. If I buy a second echo, will I need a fourth account? I really like spotify, but Amazon Music seems quite attractive at the moment.