I also don't think Lastnerve is being deliberately disrespectful - I certainly wasn't offended by the comments made or terms used, IMHO I think in a lot of cases, if the intention is good, then there is no problem with terminology used, the problem arises when the overly PC brigade make an issue where none really exists - IMHO this does no-one any favours.
& FTR as an "Invalid" I think actually lastnever makes a very valid point - I didn't read it as presumption that illness or disability makes us sexless - but that if the OPs SIL has the health & energy to be looking for & engaging with various one night stands - which requires even more effort than a loving & considered DP - then she she sure as hell has the energy/health to be looking after her own DCs.
nomore I am really glad your DH stood up & spoke out, he is a real star for doing that & I just hope your PIL do come around & see sense.
but the more I read, the more I am sure there is a Narcissistic Personality disorder going on with your DSIL - my DM is one as is my DB , so I know the signs well - a massive sense of entitlement but complete out of touch with reality & absolutely no empathy for anyone else that her actions effects - inappropriate behaviour with DCs - telling a 7 yr old she's going to have another baby in her circumstance is NOT on
& generally feeling they have a right to be the centre of everyones universe no matter who that is, or how unfair - I also wonder how much she uses her health problems to control you all - especially PIL as its a role they will find hard to break - my DM is genuinely ill, yet still constantly invents illness & will use it to control to a quite fanatical degree - this has become more & more obvious with age, but looking back it was always there
i know a lot of the time is genuine, you can tell straight away. however, sometimes (especially if the latest bloke hasn't called back) it does seem that her frame of mind is makes it more difficult for her to manage milder symptoms
I'm not saying she's not ill, but that speaks volumes - yes her state of mind can affect her health - but like the rest of us, she CAN still get on with it & cope with bringing up her own DCs - the fact that she chooses not too & feels its everyone elses job & feels is acceptable to wallow in her illness, all pity me, pity me, when life doesn't go her way, tells me that quite likely she does a lot more of that, than you & her family realise - as the DD of a Narcissist, I really feel for her poor DCs & all of you who care for her:(