Great questions to wrestle with! Your mum is right in that there is only one God (Deuteronomy 6:4, Mark 12:29). All through the Bible it’s emphasised that God is unique, that he is not like other so-called Gods, and that’s a good thing! (Deuteronomy 4:7-8)
One Bible passage is worth thinking about in particular:
The Lord’s message rang out from you not only in Macedonia and Achaia””your faith in God has become known everywhere. Therefore we do not need to say anything about it, 9 for they themselves report what kind of reception you gave us. They tell how you turned to God from idols to serve the living and true God, 10 and to wait for his Son from heaven, whom he raised from the dead””Jesus, who rescues us from the coming wrath. - 1 Thessalonians. 1:8
Here it shows that there are idols, or things that people worship, but they are not the same as the one true and living God. The idea that God appears as different figures in different religions is attractive because we don’t like to say other people are wrong. We need to be sensitive and respect our parents, but I think this idea is not found in the Bible, and would actually be really offensive to those who believe in other gods eg. a Muslim. The Bible bit above says that God sent Jesus to rescue people. Other so-called ‘gods’ aren’t like that, and haven’t done that, so they aren’t the same as the God of the Bible.
The second bit of your question opens up lots of issues. I’ll have to be brief, but feel free to send more questions if you like.
God allows people to be gay, otherwise there wouldn’t be any! He also allows people to be greedy, to steal, cheat, lie, gossip, murder etc. All these are wrong, they hurt people and they offend God and make him angry. One day God will judge people, even you and me, for the wrong things we’ve done. We need Jesus to save us. 1 Corinthians. 6:9-11. You may like to look at Sexuality.
Creation and evolution is a big topic that has been answered here before. Have a look at Creation and Evolution. Ask another question if this doesn;t answer your question.