Just because they are no longer "of this world" does not mean they don't "talk" to God. The saints in heaven are not "separated" by death from the community of the Church (Romans 8:38-39) as we are all one Body in Christ (Romans 12:5; 1 Corinthians 12:12) and Christ "abolished death" (2 Timothy 1:10 ). Therefore, the saints in Heaven can pray for us just as anyone here on Earth can. In fact, better, as they are presently in His Presence. The Virgin Mary asking God to help you should "carry more weight" so to speak than having your best friend on this earth praying for you. In fact, Christ's first public miracle was performed upon the "intercession" of His own mother (John 2:2-11).
As I say, I'm sure Catholics have an answer for this ... but as I was reading the Hahns' book and trying to explain to my wife the Catholic teaching on praying to Mary and the saints, I wasn't sure what the answer was.