mimicakey - all I know is that sounds like Pythagarus (can't even spell it!) but more than that i cannot say - my dad would be so ashamed of me - he is a mathematician
MM - I know it must be annoying to have to tone down what you feel but I think it is the only way - as MotherofZ says - she is your SIL's mum and no-one wants to hear anything bad said about their mum, however indirect and subtle - hold your head high and don't say a bad word about anyone and you will come out of it smelling of roses!