We are glad you asked this question and we appreciate the teaching your mother gave you, because it opens the door to a beautiful biblical truth about who God is.
Your mother is correct that God is everywhere, and this is firmly rooted in Scripture. The Bible teaches that God is omnipresent, meaning He is present everywhere at all times. We read in Psalm 139:7-10, Where could I go from your Spirit? Or where could I flee from your presence? If I ascend up into heaven, you are there. If I make my bed in Sheol, behold, you are there. If I take the wings of the dawn, and settle in the uttermost parts of the sea, even there your hand will lead me, and your right hand will hold me. And in Jeremiah 23:24, Can anyone hide himself in secret places so that I can’t see him? says Yahweh. Don’t I fill heaven and earth? says Yahweh. Proverbs 15:3 also tells us Yahweh’s eyes are everywhere, keeping watch on the evil and the good. There is nowhere in creation where God is not present and aware.
At the same time, the idea that God is in everything is not biblical if it means that everything is God or that God is the same as creation. That belief is called pantheism and the Bible clearly distinguishes the Creator from His creation. In Genesis 1:1 we learn God created the heavens and the earth, He is distinct and above what He made. Acts 17:24 says The God who made the world and all things in it, he, being Lord of heaven and earth, doesn’t dwell in temples made with hands. And Romans 1:25 warns against worshiping and serving the creature rather than the Creator. It is true that Acts 17:28 says For in him we live, and move, and have our being, and Colossians 1:17 says in him all things are held together, which means all creation depends on God for existence and is sustained by His power, but a tree or a rock or a person is not God Himself. God is present everywhere, but He is not everything.
The Bible also makes a distinction between God’s general presence everywhere and His special presence with His people. While God sees all and is present in all places, He dwells in a unique way with those who belong to Him through faith. And Hebrews 4:13 reminds us There is no creature that is hidden from his sight, but all things are naked and laid open before the eyes of him to whom we must give an account, so His presence everywhere also means He sees both good and evil, though He does not approve of sin and calls us to holiness.
We notice your question did not mention Jesus, and we want to gently share that it is only through Jesus Christ that we can truly know God and have fellowship with Him. Even though God is everywhere, sin has separated us from Him, and we need reconciliation. Jesus said in John 14:6, I am the way, the truth, and the life. No one comes to the Father, except through me. And Acts 4:12 teaches There is salvation in no one else, for there is no other name under heaven that is given among men, by which we must be saved. If we confess with our mouth that Jesus is Lord and believe in our heart that God raised Him from the dead, we will be saved as Romans 10:9 promises, and then God not only is around us but dwells within us by His Holy Spirit.
We pray together for you now.
Father in heaven, we thank You that You fill heaven and earth and that there is nowhere we can go where You are not present. We thank You that You see us, know us, and sustain all things by Your power. We ask that You give understanding to the one who asked this question, that they would know the difference between Your omnipresence and the false idea that creation itself is divine. Reveal Yourself as the holy Creator who is near to all who call upon You in truth. We pray that they would come to know You personally through Your Son Jesus Christ, that they would repent and believe and receive Your forgiveness and Your indwelling Spirit. Help them to walk in Your presence daily with reverence and comfort, knowing they are never alone. We ask this in the name of Jesus Christ our Lord, amen.