If you were to trim her claws you must be very careful that you only take the tipoff and not cut into the quick......the colored bit........cos that will hurt her badly.
I think she needs a lot of time and patience and although she appeared to settle very quickly this was not actually true.
I am sure she needssa attention but also space and her lashing out is just telling you and your son to stop touching me. She may also see this as a game, she scratches you pull away and she stops then comes back to play again.
A way to stop this is not to pull away I am told!! and know thats not an option for your son anyway. Another way is to distract her with a toy on a string, it maybe she hasnt got the hang of playing before and she needs to learn how to do this. I found with my late Kocka who was around 10, that she did not know how to play and the way she learnt was with my hand under the duvet............bed mice..............and moving it was irresistable and she woul pounce, bite , catch my hand which was protected by duvet.
From there we gradualted to a toy on a string and then to ping pong balls and real catnip toys.
I think she has to be taught slowly slowly and shouting or any other sorta thing like that will not help.
It could be she is still missing her kittens and so much has happened to her in such a short time..............all I can advise is to keep in touch with the rescue and take things very slowly and patiently with her.
One of my cats Sasa is a semi-feral and cannot be touched at all and I have had her over 3 years, she was previously rehomed twice but sent back for lashing out and biting and I suspect there were children involved. Actually for her to lash out at me would be a bit of a breakthrough cos she will run away if I get too close but she loves her creature comfort, she is a very beautiful looking cat and the one time she couldnt run cos she was in her tent, she patted me on the hand, not a claw in sight but that was a warning to me to stop being so close.
Franta is a gripper and a biter and he will bite for no reason and with no warning and instead of just lying his paws on my arm he will grip with claws, in and out and use me like a pin cushion. Both birmans tend to bite!
My other cat Misa the giant, is a soft and gentle boy and do not think he would ever hurt me unless he was very very scared.
I suspect that the rescue rehomed Suzie before they got to know her after being speyed and with all kittens gone, they want to free up their space so unless a cat has been with them for quite a while they do not know it very well when its circumstances change and some maybe do not understand that cats change along with their circumstances.