I'm sure your friend is sincere, but I can't agree with what she says about her church being the only one that possesses the full truth about God. No church is perfect, and in my experience, God's people can be found in many different churches and denominations.
After all, our salvation doesn't depend on our membership in a particular church (although fellowship with other believers is very important for our spiritual growth). Our salvation depends solely on Jesus Christ and what He has done for us through His death and resurrection. By His death on the cross He paid the price to redeem us from our sins, and by His resurrection He conquered death and Hell forever.
Our responsibility is to respond to what Jesus did for us by turning to Him in repentance and faith, and trusting Him alone for our salvation. The Bible's promise is clear: "Believe in the Lord Jesus, and you will be saved" (Acts 16:31). If you have truly trusted Christ for your salvation, pause right now and thank Him for giving you the gift of eternal life.
Pray for your friend, and encourage her to put her confidence in Christ alone for her salvation. Jesus said of all who believe in Him, "I give them eternal life, and ... no one can snatch them out of my hand" (John 10:28).