Shamim forwarded Din's proposal but her cousin's family turned it down.
Following a quarrel with Shamim over the issue, Din threw acid on her face and body and fled.
She was rushed to Nishtar Hospital in Multan, where she succumbed to her injuries.
Police registered a case against Din on the basis of a complaint from Shamim's husband Muhammad Yar, though no arrest has been made so far.
Pakistan recently enhanced the punishment for acid attacks, which are common, especially in Punjab province.