I might stand alone here but I agree with your friend (to an extent). Not everything can be used to worship God, and not all of our concepts of worship are acceptable to Him.

The Bible speaks of 'strange fire' being burned on the altar (Leviticus 10:1); in appearance it is the same fire, but in God's eyes it is unacceptable. Similarly, Cain's offering was refused by God because it was according to his own concept, and not God's direct revelation. Abel offered a lamb according to the principle of atonement, a foreshadowing of Christ, while Cain invented his own kind of worship and was rejected.

For example, nothing sinful could ever be offered to God - do you imagine that you could take money that had been obtained by gambling and give it to the Lord? Perhaps you could, but He would never accept it. It would be an insult to Him.

In principle, I think the same applies with worldly things, including much popular music. If something has a worldly flavor, no matter if it uses the word 'God', it might also be worldly in God's eyes.

Having said that, I don't want to come across as judgmental. I have my own discernment and my own feeling. If the Lord in you approves of something then by all means I know your heart is for the Lord, and He judges our hearts.