I had a big argument with future-in-laws

Exactly. Some ppl need to learn to differentiate between culture and Islam and just because someone's Mum says something is Islamic doesn't make it necessarily true. I used to be told so much rubbish by various desis as I was growing up as regards to Islam, that you're never allowed to disobey ur parents (of course u are if they're oppressing u or if they're making u do something unIslamic like pressurising u to marry someone u don't like, not allowing to cut ur hair (like Sikhs), so many things..).

Islamically parents/inlaws do **NOT have the right to interfere in their kids marriages,** (this is one reason living seperately is recommended where possible), yes we are meant to respect them but this does not mean they have a say in everything u do. Do ppl not understand basic common sense?? The mother has rights over her son but he also has his own rights, DIL has an obligation to look after hubby and hubby has his obligation to look out for her as well as his own parents whilst she still has an obligation to look out for hers. We aren't Hindus whose girls are expected to leave their families to 'serve' and obey their inlaws without question tho from our culture sometimes u'd never guess it..