Funny thing is when MIL visits now, DD whinges ALL day as she knows she'll get something like a cake for doing so, she's never said "No' to her.
This was a HUGE problem for us when our daughter was going through the tantrum age. We always managed our daughter's tanties well, we had a rule that if she threw one, we would not give her anything, nor would we talk to her, we would completely ignore her until she got over it. And once our daughter realised there was no reward or 'pay off' for this behaviour, she stopped doing it.

However, when my mum and dad were around, all she had to do was make any semblance of a noise, and my parents would fawn all over her, grovel at her feet, and throw toys, keys, junk mail, food at her to cheer her up. We told them that we had a rule that when our dd was throwing tanties to not reward the behaviour in any form, in other words, please ignore her, do not speak to her and especially do not give her things for it.

Well! You can just imagine, for this, we were the MEANEST parents on the face of the earth! ](*,) They completely disregarded our rules. One time, we turned up at their place, she threw herself on the floor as soon as we got there, my parents got down on the floor grovelling, saying, 'oohhh it's alright, what's wrong? Do you want a present?' I clearly and firmly said, 'please ignore her, otherwise you are rewarding this behaviour'. Did they listen? NOOOO....

So of course, the tanty went on, and she threw many more. Every time, they would give her a huge pay off for it. So, our daughter would go in as a well behaved little person, and would come out as a spoiled little tanty chucker lol. It used to take us at least a week to 'unteach' this behaviour again. Even when she grew out of tanties, she would still often get whingy after their visits, and be very disagreeable with us.

Another thing I used to have a problem with when our baby was bottlefeeding, was I would feed her a bottle, then ten minutes later she'd cry with wind, as babies do. My father would say, 'feed her again' oh yeah, great idea... I would say no, and not explain why. Why should I have to, you know? So mum would be standing there waving a rattle in her face, while I'm just trying to calm her down (Even after I asked her not to, as it was only overstimulating bubs), and dad would be yelling at me, "Feed her, can't you see she's hungry for god's sake??" Oh yes, two bottles of formula over ten minutes, what a great idea -NOT!

Ah the joys... lol