O.K. ..... I know that it can be hard to get back on the wagon after a holiday, but it CAN be done! Just start off with baby steps. Have that talk with your Mum and I am sure that she will come to the party again. You know, after reading about the egg white, there is no reason why you can't eat egg YOLK too - they have a lot of healthy nutrients in them. Just don't go over-dosing on them.
There are lots of things that you can take for your lunch - all you need do is sit and think about it. I make healthy sandwiches, slice up some apple and put in a little bag, take a piece of banana, and take a pot of reduced-fat yoghurt (but make sure that it is also not high in sugar) and that will often do me quite well. Perhaps throwing in a small handful of nuts and a couple pieces of dried fruit would be good for emergency snacking. I have healthy meat patties (made with added lentils/veges) in the freezer and will often take one of them out to thaw during the day. They are great between a couple slices of good quality bread and Avocado (as the spread). I am sure if you think about it you will think of many other things you can do/take! For the summer I have a little chilly bag which helps to keep my food cool. If it is really hot and I am going to be in the car a lot (without working air conditioner) a little freezer block helps with that, OR a small bottle of water, so I have that to sip on to help stay cool, too.
Are your friends able to have a "Picnic Day" rather than "Restaurant" - it is a heap cheaper on the pocket, and lots healthier. They may also enjoy the fact that it gives you more time to chat/walk after your meal.
Ensure that you are eating enough - a lot of people tend to UNDEReat or eat the very bare minimum, and think that skipping meals is helpful - it has a negative impact on our attempts at weight loss, tho'! Make sure that you talk with your mum and if need be, SHOW her what the portion sizes are. It may be that you would be better buying a smaller dinner plate (9" diameter) if you don't have one, and suggest that THAT is the one you would like to use! Below are a couple links - you may want to print them off to show her because a LOT of people think a serving size is a LOT bigger than it actually is! www.sparkpeople.com/community/ask_the_expe
Good luck - you CAN do this, and remember - start again with baby steps :-)