Hiya and welcome
Sorry to hear about what both you are your sister have been through. I'm new too. Different things can work for the panic attacks. heres some that work for me
1) Breath in for 3 counts and out for 5 counts for a while. Then in for 4 and out for 6 for a while. Then in for 5 and out for 7 and so on
2) Try to force yourself to get up and do something like a hobby, cleaning anything that might take your mind off the attack
3) Try to say to yourself "This is only a panic attack, it hasnt hurt me before and it wont hurt me now" - sounds daft but it works for me
Good luck with that
Take care