"Selling all" is not the act of an unregenerate person. She can't "make herself a Christian" by any means at all.

But when God gives her new birth, she won't be able to help herself - it will be her nature to "sell all" to gain Christ.

That's why we Reformed folk pray for the lost! We know that all of our own efforts are fruitless unless the Lord grants the new birth, enabling those we share the gospel with to hear it and respond with faith.

-R