Cat crying and being sick

Question
I have a 4 year old female moggy.
She has recently started crying very loudly - Normally when she looks out of the window but last couple of days being sick. She is eating and drinking.
The only other changes in her is she has started crying at the front door wanting to go out that way rather than going our the back door as usual.
We have 2 other cats - one her brother and another we got about 10 months ago who has settled in really well.
We have recently started to shut them out of our bedroom during the day when we are not home and she has started to not use her little tray - we have a big one that the 3 of them use but our female has started to wee and poo at the side of it. Normally the 2 older cats go outside to the toilet but when we are not in to let them out this happens - Any advice?

Answer
Any time a cat starts to not use the litter box is time to take them to the vets. She could very well have a bladder or kidney infection and she is trying to tell you this.

She needs a check up to find out why this behavior has started- but you must start with the physical and make sure all is well that way first, then deal with any behavioral issues if she is all clear on the physical front.