Thank you for reaching out here in the Community!
When your current plan changes to Premium Duo, you can to invite your daughter to the new plan.
You, as the plan’s manager, will be able to invite or remove members by logging into your Duo page at www.spotify.com/account/duo.
Your daughter can accept the invite, keep her current account with all the music and enjoy Premium.
For more details on Premium Duo, make sure to check out this Support Article.
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