Aggression towards sick dog

Question
We have a 6 year old Sheltie Mix (Sasha) and a 4 year old lab mix (Jewels) both rescues, both as puppies.  Jewels has been through multiple obedience classes on so on because she seems to be fearful of new situations and of any other adult outside of the family.  She is not at all fearful of children.  She is not at all fearful of myself or my husband.  Recently she has started attacking Sasha whenever Sasha shows signs of being ill.  Last night Sasha seemed as though she was going to vomit and Jewels violently attacked her.  Sasha has a vet appointment this afternoon as there was some blood in front of her ear and she is now not at all acting like herself and seems lethargic and will not let me even look at her head as it seems to be extremely painful when I try to touch it.  I am not sure what to do in this situation as at other times they get along fine and Sasha seems to be the alpha out of the 2 and Jewels typically does not challenge her authority, only when sick.  Of course last night it was so awful, it took my husband and I both to get Jewels off of Sasha and once separated, Jewels went for Sasha again and I incidentally stuck my leg out (which I did instinctively and knew I shouldn't have) and Jewels bit my leg very, very hard.  I have a 5 in x 5 in bruise on my thigh today and I am sure it bruised muscle as it hurts to walk.  Is this typical behavior and can it be stopped.  It is not an easy behavior to catch as it rarely happens, but is getting more and more violent when it does.  Sasha actually defecated while Jewels was attacking her.  I don't know what to do at all as my children, ages 6 and 8, are traumatized to think we may have to give up the dog.  Any suggestions?  Are there classes to help this type of aggression?  Can Proin cause this type of behavior as I notice she does act differently on this medication.  Thank you for any help you can give.

Answer
Hello Dayle;
I would definitely take her to get checked out on that Medication!
This would be a real key to what is going on in my opinion!
For sure take her to your Vet, and explain the situation immediately!
You do not need any more of this in your home.
Best wishes,
Melissa
Been stuck in a snow storm...sorry for being tardy!