Hey there,
When you miss a payment of any Spotify plan your, and in your case all Family accounts will change to Spotify Free accounts.
In this process, no playlist will get lost.
When you upgrade your account to Family again and invite your wife's existing account, the same process happens: When your wife accepts the invitation, her account will be upgraded and her playlists will stay in the account.
Let me know how it goes and have a nice day!
Luke
Hey there you, Yeah, you! 😁 Welcome - we're glad you joined the Spotify Community! While you here, let's have a fun game…