When to make crib into toddler bed?

I have Irish twins, obviously I’m getting my son his own crib, however his sister will be 1 in 11 days! :) I know she’s still super tiny, however I’m thinking ahead. When should I make her crib into a toddler bed? She stands in her crib every day and suddenly she’s having an issue with sleeping in it. I’m not sure why, however I know it’ll be for sure time when she starts climbing out! She hasn’t tried yet, but I also know she’ll be walking soon.

So mommas, when is it time for my baby to have her big girl toddler rail? :)