Rufus just spewed up

Rufus was sitting on the couch watching Gordon Ramsey when she started miaowing very loudly.  She jumped onto the floor and did three huge vomits.  Two on the hallway rug and one out in the kitchen.  Earlier on she had eaten two small cans of dine or fancy feast.  She barely ever eats anything - I don't think the conditions are right for her to eat.  She favors her own dish, but Pachuco always comes and nudges in, he's worried about missing out - even though he has the same food on his dish.  

I am worried that Rufus is sick!  She has been drinking water from a glass (she is doing it right now!), but not huge amounts.  I took her to the vet because we had decided to give her more affection each day and this resulted in her killing and eating a mouse every night.  I was worried that the mice and rats were poisoning her and that it was why she wanted to drink the water.  The vet suggested diabetes and tried to get a urine sample by stabbing her with a needle in the bladder realm. It was a terrible experience for all and no sample was achieved, making it all useless.  He sent me home with a syringe to get my own sample from a litter tray, but how am I supposed to tell which cat wee is which?  When there are so many cats! I just want her to be happy, but she won't come under the covers at night, instead prefers to be out in the cold 10 degree night.  She used to be different.

She is a tiny waif of a thing, probably weighs about 500g.  Light as a feather.  But she is an adult cat of 7 years.  It is our goal to make her as fat as the Mooch, by providing her with the ideal conditions and tastiest snacks for eating.  We decided it tonight, but it hasn't gotten off to a very good start with all this spewing.  I'm not even sure how all that food could fit in her stomach.  Maybe she just got excited and ate too much.  It is a real worry.