The UK won't recognise her time in the Netherlands towards her Citizenship/ILR/etc. Now depending on how long you are away, she may get permenent residence when she returns. Currently once you have been married for > 4 years she would get an ILR upon successful application, if you hadn't reached that point she would need to apply for an FLR for a 27th month period. She would then need to reside in the UK for 3 years to gain her full Citizenship.
The concept is that they only want to give residence/Citizenship to those who intend to settle and stay in the UK.
One other thing is that right now it is difficult to plan for the future, because of the looming changes that would likely effect, in some cases to a great extent, the information provided above. I know Vicky constantly says "nothing is in stone" which is true, but it has become impossible for families to plan how and where they are going to settle and know what sort of hoops they will have to jump through. Case in point, I had to make a serious decision about waiting in the UK for my citizenship or working for my company somewhere else in the world. The thing is that the working elsewhere will probablly not be forever as we both feel strong ties to the UK, and I can wait around for another year, but some of the proposed changes would make me wait at least 1 year longer then I had planned to become a Citizen and that totally changes the dynamics. We had been doing personal planning on one timeline as well as my professional career development, but to have the pulled out from under you makes it difficult. I know it is a side rant, but here is another example of a couple who won't be able to properly plan for their family.
Also, just from a pratical standpoint, you realise the NL have some of the most heavy taxes out there... Basically the tax everyone to the point of equality, so don't have any grand aspirations of making a shedload of money there.
