My cat is hissing a lot

Recently we went out of town and gad a friend stay with our cat as we always do and the same person always. Coming home this time we noticed a change in her behavior and right away she was not happy when we picked her up. She loves to be petted and stroked under her chin but this time provoked hissing and a bite which she never does.
This morning I tried putting her collar on and she hissed again several times and tried to bite me.
I am wondering why she would suddenly start acting out this way. I am worried there was some trauma while were gone but this friend is very good with her usually.

Have you been in contact with this friend who was taking care of your cat?   They might have some information which would explain things:  perhaps our cat's behaviour was strange with them too, or they are aware of something which happened which could have frightened the cat.

It could also be that your cat is unwell or in pain in some way so I suggest you check information with your friend as soon as you can and if you do not get clear information which explains the change try to take your cat to the vet as soon as possible for a check over.  While it could be something as simple as an unfamiliar scent on you when you returned home it is better to be safe than sorry and not assume this unless she settles very quickly.

I hope it turns out to be something really simple, your cat is fine, and back to usual behaviours with you very soon.

Could it be that she's mad at you for leaving her? I have a male tabby like this. He is normally very friendly but there have been times he will hiss for a few days, if something happens he doesn't like. I would suggest giving her some space for a few days and let her come to you and see if she gets better.