If anything...
This means he was ready to benaquab her...Traditionally Dupatta is a symbol of a woman's dignity...the veil that protects her, must be respected to respect a woman's character...Sahir is gesturing that Arzoo has bad character...and he is ready to take that veil off...
OrIt was simply a step in Sahirs seduction of Arzoo...
that is a very valid explanation and also thoughtful.