Colombia to UK Visas

My girlfriend and I have been together for 2 years and I would like tobring her to visit my friends and family.

As always the government websites are very confusing. Has anyone here already done this, if so please could you say which visa you applied for and what you needed to do? I believe we have a few options as not only have we been together for 2 years but; I have a residency visa for Colombia, we have an official letter proving our relationship status ( similar to a civil partnership) and her father has Spanish/Colombian dual nationality currently living in London along with his sister.

Thanks!

Phil

Why would she need proof of a relationship for a tourist visa to the UK??

We needed proof of the relationship to get my residency visa for Colombia not for her visa. Once she has stayed in the uk for the 6 months we will make the decision whether we want to settle there or not so we could be looking at a spouse visa after.