Argentina - UK... Some straight answers please

Hi there everyone,

Firstly, I'm a bit new to all of this so I'm sorry if I'm asking something that may have been answered amongst the other pages (please feel free to point me in the right direction).

I've read all the info on the UK Boarder Protection sites and unfortunately it's left me even more confused. I've tried to look for answers on the Argentina sites but that too hasn't left me with much confidence for what we actually need to do.

I suppose I should explain all...
My future wife and I are hoping to get married in the US within the next 6 months. If everything goes to plan then I'm looking for straight answers about:

How she can come to the UK?
Is she entitled to become a BC or BN as I am and have been since birth?
Could she be both Argentinean and British?
If her mother is Spanish does this mean that she has any rights to the EU?

I know that if she meets all the criteria that she is allowed to stay in the UK, once application is approved, for a two year 'probationary' period before being allowed the right to live and work indefinitely but are there any restrictions to her coming here, living and working in the first place?

All answers would be appreciated as we're both not sure where to go from here.

Thanks very much