My first bit of advice would be to say stuff her and stick to your program as usual.But I know how hard that could be so better to be prepared.
I would have cereal with skim milk for breakfast -porridge or special k is good. Or choose an egg on toast - use grainy bread. Have a cup of tea with it.
Have a piece of fruit for morning tea.
Lunch have a salad with protein like ham or chicken. If you are out and about try subway salads.
Afternoon tea have another piece of fruit.
For dinner have your meat and veges and ask them to leave off the potatos or just don't eat them. You could also try a stir fry vege dish or
For dessert have a yoghurt or fruit salad or skip it all together.
Make sure you drink plenty of water. And for drinks when out you can have diet coke or coke zero without doing any damage.
Keep a bag of sugar free lollies in your handbag too.
The main thing will be to keep busy during the day so that you are not always sitting about eating. Try to get out and about walking as much as possible.
Godo luck and I hope it all works out for you.

ON TF MAINTENANCE SINCE 11/08/09
v In 42 weeks (14/10/08 – 10/8/09) I lost 38.4 kilos. And on maintenance I lost another 2 kgs.
v TOTAL WEIGHT LOST 40.5 KILOS!
v I started at 110.4 kilos and dropped to 72 kgs. I am now 70kgs.
v My waist measurement dropped 24cm from 98 cm to 74cm.
v I started out as a size 18/20 top & 22/24 bottom. I am now a size 10-14.
v My BMI was 39.2 which was obese. I am now in a healthy weight range.
v THANKS TF I COULDN’T HAVE DONE IT WITHOUT YOU!!