Answer:
The princesses' actions were cruel.
Step-by-step explanation:
The original sentence doesn't have the apostrophe and es after 'princess'. The reason for the apostrophe and 'es' is because it makes it possessive. The actions were of the princess's so it was hers.
I hope that makes some sort of sense :)
FYI there's a website called grammarly that you can use to check your grammar for like papers, emails, etc.