The tourist visa is very low cost and very quick for a decision.
I always advise folk to make as good an application as they can and just do it. There are no high risk impacts.

Your g/f will need to clearly demonstrate that she has strong ties and compelling reasons to return home within the visa validity, that in the eyes of the ECO will on balance outweigh any reasons to remain.

Just search here on the forum there's huge amounts of valuable information.