Ruth, it definitely won't be buffet ... most lilkely a sit down 3 course meal

... so yes, tricky!
Lexxiss, yes, I've experienced dinner at their house many times before, and as we've always taken wine in the past, she'd probably think it was a bit strange if I called her on this occasion to ask what was being served. I guess I'm just going to have to hope that there's plenty of veggies or salad to help myself to and be careful with small portions of anything else, so as not to offend. The hardest thing is going to be dessert, not because I don't have the will power to go without, but because she knows me so well and knows that normally I would never, EVER, turn down dessert

Oh well, there's a first time for everything!