Toddler bed

My daughter is 14 months and her lil sister will be here in a little less than 2 months. Her sister will be in a bassinet for probably 2-3 months. (At least that’s how long my first used it) but then she will move to the crib and my daughter will have to move to a toddler bed. I’m wondering when I should move my daughter to the toddler bed to get her use to it. She still has like 4 months until she has to move but I don’t want it to be a huge issue with the new baby and everything being new for her.