Switching to Toddler Bed

Ol

My DD is 15 months, she will no longer nap in her swing so she is now napping in her crib. I am wondering when most parents put their child in a toddler bed, by this i mean i have a convertible crib where on rail comes off and becomes like a half rail.

My DD loves sleeping in my bed and fights me sleeping in her own bed. I wonder if she’s too small to put the side rail on and just let her come and go out of her crib as she pleases at night.