Sisters lies - am i in the wrong?

My older sister who is almost 30 has a boyfriend my parents arent happy about as he is from a different background. We obviously don't agree with their POV but they're also conservative and don't agree with sex or living together before marriage.

My sister has just moved in with her boyfriend abroad (they plan to marry - but no concrete plans yet) and we were going to visit and stay with her during a holiday, and she planned to still keep it a secret and her boyfriend would go somewhere else at that time. I told her this was quite twisted as its a big lie right under their nose.

In our family chat group she even sent photos of the new vew of her flat, and i said to her is she really showing it off since there's a big lie there? and she called me nasty.

Am i in the wrong? we are all adults here, and my parents POV is wrong but i think my sister should have the courage to tell the truth. I think its a bit twisted to overshare and act like its rainbows and butterflies like my parents are actual fools. We dont have to agree with them but at least respect how important it is to them and treat it with a bit more seriousness.

no ur not wrong i am muslim even our religion doesnt allow this if her boyfriend loves her then they should get married then they can stay together

i dont have an issue with them living together, i don't think they have to be married. II have an issue with how shes going about it and lying to my parents.