Imagine15, welcome to TCS!
Is your cat constipated or have she had enough water to keep her hydrated and did she swallow something like a cord or piece string or yarn?
Please do not pull the poo out as it may cause further injury to the anus as the poo is dry and hard.
Please bring her in to the vet for an assessment and the vet has a way to remove the stuck poo.
Keep us posted after the visit to vet.