I want to build one bridge splitter contract with interaction of LI.FI protocol. Will LI.FI’s contract be called from senders wallet or can a swap be done between a 3rd party contract between sender and receiver?

Some tools may have protections not to do the same action multiple times. This is important as bridges mostly track transfers based on the transaction hash.

An option may also be to split on the destination after the bridging using this API we provide:https://docs.li.fi/li.fi-api/xchain-contract-calls