Initially your best starting point would be for her to come as a visitor for 6 months. If you haven't met her, it will not be possible for her to come to live with you as all settlement visas require you to have met. This will also give you the opportunity to make sure that you do want to be together once you are with each other every day.
If you decide that you do want to be together having lived together for 6 months, then she will need to return to Columbia and make an application for a fiance visa as it is not possible to switch from a visitors visa to a spouses visa in the UK. It is also generally not permitted to marry in the UK on a visitors visa. You will need a certificate of approval which you are not guaranteed to get as she will be on a visa of less than 6 months. It may be possible to marry in a Church of England where you don't need a certificate of approval, however this will be entirely up to your vicar and the diocesan registrar and they are not forced to say yes.
I hope this answers your question in which case please Accept. If you require further information, please ask.
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