Why was Rebekah willing to meet Abraham's servant at the right time?
Rebekah was willing because God, in His foreknowledge, knew she would be willing. Her timely meeting with Abraham's servant was the sovereign working of God, yet she acted willingly. Divine foreknowledge and human free will operate together: God knows what an individual will do with His particular offer, and He chooses accordingly.
Les teaches that the sovereignty of God and the free will of man run from Genesis through Revelation, and 1 Peter 1:2 identifies the elect as chosen according to foreknowledge. God can choose some and not others because He knows what an individual will do with His particular offer of salvation. Rebekah came to water the livestock and met Abraham's servant at just the appropriate time. It was the sovereign working of God, but she was willing. She was willing and chosen because God knew she would be willing. Likewise, believers are not saved because they were special or better; God in His foreknowledge saw what they would do with the offer of salvation.
And the servant said unto him, Peradventure the woman will not be willing to follow me unto this land: must I needs bring thy son again unto the land from whence thou camest?