I think everyone has been subject to sabotage at some point, I know I have. A friend or family member encouraging you to stop losing weight or for you to have a day off plan.
Some friends and family will be doing this intentionally because they are worried about you, some will do it intentionally because they are jealous and other will do it without even realising they are doing it.
The problem is, how do I get around this? Getting around this will not always be simple, the first step is to say no, simple say you do not want whatever they are offering you, they may take offence or be unhappy with you, just explain, explain your doing very well at the moment and you do not want to ruin your hard work. You do not have to be left out, for example if your at a coffee shop and they are eating cakes, have a fruit salad or offer to share with someone so its half the portion.
If you have explain before and they still are not getting it and their sabotaging efforts are getting more regular, have a word with them. Maybe they do realise they are doing it and will be shocked when you speak to them, when you have spoke to them they may realise that they are upsetting you and stop it. If they do realise and are not willing to stop (which I find unlikely) you can discuss their reasons. You can explain your happy losing the weight, you can tell them why you are losing the weight and reassure them that it is healthy and you will not go too far.