query: making someone use seller's title company in PA

I'm unaware of any PA statute prohibiting a seller from negotiating the requirement in a contract. If the buyer agrees, then I guess they use the seller's title company.

Now, that said, if the transaction falls under RESPA, then the seller may only select the title company IF the seller is paying for the title insurance.

Transactions that fall under RESPA are most typically residential 1 to 4 family dwellings that are being mortgaged by an institutional lender.