Hi, i put a post on here a while ago about my dog refusing to eat, and we didn't change her food for a couple more weeks, but she has just thrown up twice in the garden, she is starting to get thin, and we are getting quite worried one second she loves a food and the next she refuses to eat it. We have frolic royal canine and bakers in the cupboard and wont eat any of it. 
Any tips would be great

Btw she does eat, but only the tinyist amounts

Have you had her checked at the vets for any blockages if she is vomiting after food??

No we havent but thanks we will do that

Definitely check with the vet.  Until then feed her very small amounts of food several times a day.  I would stick to cooked chicken for the time being until she gets a clean bill of health.