Hi there Sylivia,
It is possible, in the early stages to give Millie the help she needs at home.
Things to discuss with vet
1) as some have mentioned, dehydration is a factor, so learning how to give Subq fluids at home if she's dehydrated can be helpful, perhaps you can get the vet to show you.
2) Assist feeding, and getting as many calories as you can get into Millie is important, this might involve giving her some higher calorie (perhaps a recovery food may be suitable in the short term speak to your vet about those) DKA is more likely if cat is not getting enough calories.
3) Possible infection inflammation? check teeth/UTI/pancreatitis??? Vet will need to examine Millie to try and determine if anything else is going on, urine analysis/pancreatitis test
4) Millie's dose may well need adjusting, if she is not getting enough insulin this can also be a factor in recurring DKA, but with the data you have at the moment I don't feel comfortable suggesting an increase in dose, I would suggest that aside from testing amps and pmps, that you get a couple of readings on every cycle (am and pm) to give you an idea if Millie is staying high all the time or if she is in fact dropping somewhere in the cycle and then jumping back up (bouncing) by the next PS. The 2u got her down to 160 a while ago (and she may have gone lower, earlier in that cycle) given that she bounced up to pink by +2, that's not to say that this dose is still 'working for her'
Here is a link to a post that might help with how to entice Millie into eating, there's also a link to feeding tubes, which is another option that is used when a cat won't eat and you need to get food and insulin into them.
http://www.felinediabetes.com/FDMB/threads/suggestions-on-how-to-stimulate-kittys-appetite.130770/