Being made to have an Engagement just so my parents can have piece of mind

Good Morning all

Forgive my punctuation and grammar in this post as I am rushing to write this out

I (M25) have been seeing this girl via Uni for about 5 years, recently I moved out my parents home to live closer to my work, and I invited this girl to move in with me as we love each other

Neither of us are practicing Muslims and are ExMuslim by definition

My parents did a surprise visit this week and met my partner for the first time

They were respectful and asked to speak with me later, which I did

They said I should compromise and engage with this person so I don't live in sin according to Islam; and that other kids have been disowned for not doing so

Whilst my parents do not know I've left the religion, I haven't been apart of the religion since I was a young boy (about 10 years of age)

What will I gain from not telling them? I do not want me or my partner to pretend all our lives- or have a big fancy islamic wedding for the sake of my parents

Anyone in a similar situation or can offer any advice? Thanks!