Hi Kev, welcome to Filipino UK

The new online application website is very different to the the old one. There's been many issues to resolve.

Right now there are too many permutations for anyone to go through all possibilities. Sorry can't be too much help on specific questions.

That 'Personal Details' Form VAF4A is a generic 'one-size-fits-all' form which all applicants complete.

Your wife needs to complete it solely for HER details unless where specifically stated otherwise.

You're right that the Sponsor Details realtionship drop down menu does not include anything for Husband, Wife, Fiance(e), civil partner etc which does seem odd and is extremely confusing and frustrating.

On the paper forms it does state:-
..The sponsor is the relative that you will live with and be dependant on in the United Kingdom
So it's possible that the correct selection from the drop down menu is 'Other Relative' but it's not clear at all..IMGO

I think your best approach is with a phone call to UKBA for a definitive answer.

Any feedback from your side on their response would be helpful.