Having looked only at the title ("royal cinderella mama") and avoided the synopsis (so it couldn't spoil my hilarious & obvious misinterpretation), am I correct to interpret this as being a story about:
A prince going around looking for which lady has a perfect fit for his d***, after a night of passion that ended when the bell struck midnight (could also be a dildo that fell out when she ran down the stairs, I guess)? And mc's stepsisters cuts their body to forcefully making the fit snug, ignoring the pain and blood and permanent disfigurement in the pursuit of becoming a queen?
And this night of passion having ended up with permanent consequences, so cinderella becomes a [single?] mother?