I'm glad you don't feel guilty, and you shouldn't! You've achieved so much by staying 100% for 50 days, and like LED says, one day off isn't going to hurt - but letting one day turn into 2/3 days at regular intervals is.
This is NOT a morale victory for you family, and don't give them the satisfaction of thinking it is. This is a weightloss ACHIEVEMENT for you, because you have enough self-control and insight into your problems that a) you are making a sustained effort to lose weight in order to become the person you want to be b) you have kept yourself committed to this effort despite people attempting to erode your will-power and confidence in yourself by telling you you'll never manage to carry though on your plans c) you recognise your achievement to date and rather than spiralling into negative feeling of "failure" for an unplanned one day off, you've acknowledged to yourself that it was not an inappropriate reward for all the times you have denied yourself over the past 50 days, and have drawn a line under the incident.
Those are all real achievements that are going to contribute massively to you getting the rest of the weight off, and more importantly, keeping it off!
You can't stay on Exante forever, and what you've proved to yourself is that when you come off Exante for good and start eating things like garlic bread again, you'll be able to eat appropriate amounts of these things that you enjoy rather than a mountainous plateful that'd have your body's fat cells working overtime.
Hope you enjoyed the inadvertent treat last night, and hope your Mum gets better soon and the stresses in your life improve as well.