My friends cat keeps biting her?

My friend has a 3year old cat that she got from a kitten. The cat never goes out and is stuck in a one bedroom flat.

I don't agree with cats being locked up in flats. I think it is in any animals nature to explore.

She does not like being picked up and when my friend strokes her she suddenly turns. Well she has bitten my friend 10 times to my knowledge and her hand has swelled up. She even scratched her when my friend was sleeping.

I feel that she is bored and would be happier being rehomed to a house with a garden as she rattles the letterbox to go out onto the landing.

I say this cos there is a cat where I live who goes out when he likes. He always comes up to me for a bit of fuss and he seems very laid back. I think it is cos he has freedom.

I don't want to upset my friend but I feel I should say "your cat is bored. She knows to live in a house with a garden".

I have implied it and my friend said there is no way she could get rid of her.

Any ideas?