Honestly, diet pills and diet shakes and diet meals.. it's all about money. Don't bother! You only have to browse around on these forums and see the million posts/advertisements of 1-post-people trying to sell pills and shakes to realise it's suspicious. This is coming from someone who fell for all that bullshit and tried most of the above... and had very limited success. (And gained the little weight I'd lost back anyway.) They always say 'to be taken along with proper diet and exercise', but fact is, with proper diet and exercise you'll be losing weight anyway.
As much as we all wish it was so, there is no quick fix to losing weight... You gotta just stick to it consistantly, and however long it takes, it takes!
Your mum and sister should just be happy and supportive of you, not trying to push manufactured products on you. The 'healthy' amount of weight you should be aiming to lose each week is 2lbs. Dropping more than that means you're likely either dropping water or muscle - water you'll likely gain back once you rehydrate, and losing muscle lowers your metabolism and makes it tougher for you to lose in the long run.
Good on you for doing this yourself, your own way! Good luck! Start a diary and let us support you too!