Toddler bed age?

Aly • Happily married. MC 4/2015👼🏻Baby girl 10/2016 💕 baby boy due 2/2018 💙

Hey mamas!

So my baby girl will be 16 months when #2 is due. We bought a convertible crib for her. Do we buy a new crib for the new baby and keep her in her current crib , or would we be able to buy a new toddler bed for her when baby arrives? I'm not sure how old she needs to be before she's out of the crib! Thanks!