How do I ask my gogo to stop switching to English when I try to speak Zulu?

I grew up hearing Zulu around the house, but I never spoke it back. Now that I’m trying to learn properly to connect with my family, my gogo just laughs kindly and switches back to English because I’m hesitating too much. I want to tell her I need to practice real conversations, but I don't want to be rude. Would it be better to get some solo practice time with an AI tool like Chickytutor.com to build up my confidence before I insist on 'Zulu-only' time with her?