Hey @user-removed! Welcome to the Spotify Community. ^^
That doesn't sound quite right.
Make sure to use your username rather than your email address when logging in from the app.
Sometimes it helps also to use an older password.
Let us know if that helps, thanks! ^^
It would be great if you could give us these details:
1. Exact Device (e.g. Samsung Galaxy 4)
2. Exact operating system (e.g. 4.4.2)
3. Spotify app version installed (2.0.0)
I've escalated your issue to the support.
I will reply on this thread with help soon. ^^
Can you try logging into your account rather than to the app?
It'll be better if you use your email instead of her username for this, just to confirm which of the two (password or username is the issue).
If you get the same message you need to reset the password. ^^