I'm looking to bring my gf here on a Fiancee visa however she is married and we still need to get her an annulment before we can apply. If it seems that the Annulment is going to take a while can we apply for a visitors visa for her instead of the Fiancee visa?

If so please could someone tell me how much the visitors visa will cost and how long can she stay here on that particular visa and how long will she have to leave the UK for before we can reapply for another visitors visa?

Also will applying for this visa effect our application once we come to finally apply for a fiancee visa? Info on this would be greatly appreciated as I'm really trying to explore all avenues so I have a plan B should things take a turn for the worse.