Only God knows her heart, of course, and whether or not she ever believed in God, or if she's just been going through the motions all these years without actually believing in Him.
But whatever her past has been, it's clear now that even if she did believe in God at one time, her belief was shallow and didn't reach into the deepest parts of her life. True belief, the Bible says, leads us to commitment -- a commitment of our whole lives to God, and to His Son Jesus Christ. Jesus said, "If you love me, you will obey what I command" (John 14:15).
When I hear of someone like this I'm reminded of Jesus' parable of the sower. (You can read it in Luke 8:4-15.) In it, Jesus told about a farmer who sowed seed in his field, hoping for a good crop. But some seed fell among rocks, where it soon withered away because its roots couldn't penetrate the rocky soil. Other seed fell among thorns, which choked off the young plants. Other seed, however, landed on fertile soil and produced a bountiful crop. This, Jesus said, is a picture of the way people respond to the Gospel. They hear about Christ and His love for them -- but some reject Him, or allow the cares of this world to cut off their faith. Pray for your friend, that God will convict her of her sin, and cause her to repent and commit her life to Christ.