hi Dave,
welcome to the forum..I am pleased that u have had a great time during ur visit here in our country though there's some typhoon experience..
about ur visa queeries, like LadyJ have said we already do have lots of posts here about it..u just have to use the search button here..
if u decide to have the visit visa, ur friend should have bank accounts, properties and a stable job so to prove the ECO that she can support herself during her stay in the UK and she has the reason to come back home..u might say u are willing to sponsor her, it is ok but she really needs to have that to prove that she will not depend on public funds..
Goodluck..
