Charles Spurgeon Commentary Acts 16:14-15

"And a certain woman named Lydia, a seller of purple of the city of Thyatira, one that worshipped God, heard us: whose heart the Lord opened to give heed unto the things which were spoken by Paul. And when she was baptized, and her household, she besought us, saying, If ye have judged me to be faithful to the Lord, come into my house, and abide [there]. And she constrained us." — Acts 16:14-15 (ASV)

And a certain woman named Lydia, a seller of purple, of the city of Thyatira, which worshipped God, heard us: whose heart the Lord opened, that she attended unto the things which were spoken of Paul. And when she was baptized, (Acts 16:14–15).

She seems to have become a believer in Christ, and to have been baptized at once.