My cat doesn't like to have his claw cut. The only it can be done is when he is given a sedative. Your friend can ask the vet for some medication. Once my cat is relaxed, I can trim his claws with a hand held nail trimmer. You have to be careful and only trim off the tip of the claw.
I know what a jealous cat is like. It takes time to assure them that you are not to steel the love of their life away from them.
Where does the cat bite you in the middle of the night when you are sleeping?
I agree! And I was thinking it may also be that your overnight guest is talking in their sleep or has sleep apnea - a cat catches these things! ~ Morgen