Bedtime with a toddler

Victoria
So my fiance has a daughter of a previous marriage. She is 4 about to be 5 years old. She has her own bedroom with night lights. Sometimes she goes to our bedroom and my fiancé wants her to sleep with us. I get so mad at him, I'm 7 months pregnant and move all the time and with a toddler their I cant. Her mom send me a message saying I was crossing the line by letting her sleep with us. Several mom's have told me never let a toddler in your bed because she will never sleep in her own bed. Am I being to strike with her? It's it so wrong that I want some space away from her?