My Cat Killed A Squirrell Last Night She Is Normally

my cat killed a squirrell last night she is normally a house cat but she got out yesterday in the middle of the night she went to the bathroom all over my clothes and she is very very good about using the box today she's constantly running to the box and has started throwing up she is also extremely tired she's scaring me this is a cat Ive had since she was born I even bottle fed her and shes 8 years old now....what could be wrong should I be scared like I am???