Taking credit for other's work

We have all come across situations wherein somebody takes credit for something that he or she has not done. Infact not just at work, but also within your own home you come across such situations. Here are 2 situations that I came across in the recent months:

Situation 1: The Inlaws/Outlaws house at Bangalore
One of the days when we were vacationing in Bangalore, my MIL asked her loving son as to what he was craving to eat, her son duly said rava idly and sagoo. My MIL said she will ask her daughter (my SIL) to make the sagoo as she makes the best sagoo in the whole world. I pitched in to help, I cut the onions, cut and peeled the potatoes and cooked them in the pressure cooker. I also dry roasted and ground the ingredients. My MIL did the tadka/seasoning and added the ground paste and the potatoes and let it cook for some time, my SIL who had vanished into her room came by then and stirred it a little bit and tasted it and said it tastes great. My MIL asked her son how it tasted and he said S's sagoo is indeed the best (!). To this day I tease hubby every time he asks me to make S's sagoo. I ask him "you mean the sagoo where in I cut the onions, I cooked the potatoes, I roasted and ground the masala and your mom did the tadka, that sagoo right?".

Situation 2: My Company
I am leading the process improvement functions for some of the products within the company and recently I implemented many initiatives within my group, as a result of which the performance of some of the product lines has gone up to a great extent. My Director who also happens to be an indian got very insecure because of the praise I was getting from other business leads. I was supposed to meet with the COO to submit my recommendations on a bunch of initiatives that we were planning to execute in UK and Singapore, my Director scheduled the meeting and conveniently "forgot" to include me in the invite. She went ahead and presented my recommendations. I had a feeling something like this would happen so I "conveniently" forgot to add the data justification slides to the presentation deck. As a result of which she was left in a lurch and she had no choice but call me in the middle of the presentation to answer the questions that the COO had asked. Finally at the end of the meeting my COO was convinced that it was I who had developed the deck and not my Director. I feel bad doing this, but I couldn't think of any other alternative. I am pretty sure now she will be very careful movign forward. The other good thing is that I have been asked to lead another team within the same company so I will no longer be interacting with this mean attention craving Director.