She is being rude and controlling. Her pretending to be charming and polite does not make her behaviour acceptable. It is clearly making you feel uncomfortable, so she needs to be put in her place and the grans here have suggested some great options for dealing with her (lack of) manners. There is no reason why you should put up with her ongoing passive aggressive superior attitude. Perhaps next time she gives you a skinny portion of cake, you should ask her whether it is rationed.
Hysteroscopy using spinal block/epidural
By special request, let’s discuss our favourite Classic Music and why?


. She's not openly rude about it, and she's not a mean person so I know it's not coming from a bad place. It started off as being amusing and now has become really annoying! She'll give me the (noticeably) smallest slice of cake. Or make a point of having salads for lunch when we come over. The bread is placed on the other side of the table and when I ask for it to be passed to me she'll be all charming but pointedly ask me if I think that's really such a good idea? I'm overweight, admittedly, I enjoy my food. But I'm nowhere near obese and my doctor has never cautioned me or told me to lose weight. I'm a happy (if slightly heavy) woman. I don't really now how to bring this up with her without things becoming really uncomfortable.
. I'm not terribly upset by her behaviour - I just find it annoying. I know I'm...round...yes a tad over the BMI but not (excuse the pun) hugely. I think I will take the advice to have a quiet word with her and try to make her understand it's not on. When do they stop treating us like grown-ups
