.............. makes perfect sense ... theoretically!
Alas - as you'll have already gathered (based on two of our members' recent experiences) - obtaining a Visitor Visa isn't, in practice, quite so straightforward as it might, at first, seem ... despite each of the applicant's honourable intentions. Likewise, of course, you will, by now, have discovered the MAIN reason(s) as to WHY this's so.
But not ALL applicants are unsuccessful. And (who knows?) your g/f may possibly even be among the lucky ones.
So ...... for about a tenth of the cost of a Settlement Visa, it could well be worthwhile "taking the bull by the horns"!!