Help day time nap

[Pulpfiction1]

Dd is 16 months. Tbh I've let her get away with too much. She went into her own room at 9 months and after about a week sleep training she started settling and sleeping through with no fuss. But day time naps have always been an issue. She either sleeps in the car, the pram or breastfeeding.

Car and pram sleeps are not really practicle now due to lock down and I've recently stopped breastfeeding as I had had enough.

I'm due another baby in Oct and I need dd to start taking her day time nap in her cot not in me. But how? I put her to bed and she just goes hysterical. Shes been in there 20 mins now and she's still going strong. I've tried soothing her, singing to her but she won't have it.

Any tips please? Dh says it's too late we've made a rod for our own backs with her and the new baby will just have to learn to sleep in a cot from day one.