Remember that things like this are a pita for employers and they want the whole thing to go away. Basically it's her word against yours, so unless some independent third party shows up, the employer has no evidence to do anything.
As above, take someone with you if possible.
Take notes
Start off asking what the procedure is, what the next step is Ask what your rights are, ask whether it's appropriate that you consult a solicitor
Ask what you've been accused of and I mean specifics - you were rubbing up against her, eh? How? In what way?... an ordinary crowded way or a sexual way? A sexual way huh? How was it sexual? What she may regard as sexual may be cultural thing (well....maybe not)
Get dates times etc...ask for details of at least 5 separate instances...nothing vague like "wednesday morning" but specifics, you know Colonel Mustard in the Library with the lead piping (fnaar) @9:15 yesterday. Her being at all vague amounts to heresay and isn't good enough.
At this point, don't get drawn into making rebuttals of specific accusations, take a deep breath and ask for her evidence. Save your comeback for the next stage (hopefully there won't be one)
If she believed this was happening, why didn't she tell you to stop (major omission on her part- are you an intimidating charatcter?). Why didn't she get your/her supervisor involved - had she had informal conversations with supervisors (if not, why not - how the hell were you supposed to know there was a problem and now she's gone all nuclear).
Make a very stong point about her getting her husband involved and say you were harassed and intimidated by him - was it on company premises? - an employer has a duty to protect it's employees and that includes you. Is he waiting outside in the car to harass you after? Say you are concerned for your personal safety
To any accusation, complete denial is irrefutable unless she has some other impartial evidence...do you have cctv in the restuarant? Has it been checked?
If what your friend says is true about this happening before, bring this up at the end saying you have been told this has happened before - ask them if this is true. If they deny it your quote should be "So you are 100% telling me that this sort of thing has never happened before?" Make sure you get an affirmitive from both company reps individually
Good luck - just keep in mind that the only person who's present who wants this meeting is her. You don't want it, and neither do your employers