This is a Duolingo system-side issue which the course team does not control. You may want to comment in one of the general Duo forums, e.g, Troubleshooting. I've only recently begun to see complaints of this type, so maybe something has changed, and Duo considers this... generosity... as an "improvement."
I believe "my girl" could mean "my daughter" in English, under the right circumstances, and it can also mean "my friend", right?
In Czech, "moje děvče" and "moje dívka" is only my girlfriend. "Moje holka" is either girlfriend or daughter. None of them would be used for just "friend".
"Přítelkyně" used to mean a female friend, but that's kinda obsolete now. Someone may still use it to mean female friend if they're speaking in a high register. In casual/regular speech, it will be interpreted as "girlfriend" - and even in that meaning it sounds a little uptight. Young people will say "moje holka" or "moje mladá", for example.