It's good that you've made another appt if you think the diarreah is worse
for that and if they didn't test the T4 I would definately recommend having it checked.
Vomiting and diarreah together is a concern for dehydration as the cats lose a lot of water from each, especially when it goes on for a while. Are you familiar with the skin tent/pinch test? With you thumb & first finger gently pull up the skin on the back of the neck or between the shoulder blades and let go, if the skin snaps back to normal right away or within 2 seconds she is not or maybe just minimally dehydrated. If the skin takes longer than 3 seconds or stays tented she is dehydrated & may need some assistance with fluids.
I'm glad Pinky is on canned
Has the scratching/fur pulling stopped since she's been on the mixed grill?
How much food is she eating in a day? Have you increased her daily portion at all to see if that helps with the eating other things or stealing the other cats food?
If you can put a lid on the garbage can or put it in a cupboard or something to try to keep her out of it, attempting to eat the floss especially, concerns me as it can get wrapped around the intestines & cut off blood flow.
A number of symptoms point towards HyperThyroidism however there are always similiar symptom possibilities.