My mom loves colouring books too, they're really complex and more meant for adults (I'm sure a kid would enjoy them too though lol). She finds it very relaxing.
I wouldn't say it's all thanks to me helping you out once or twice x//3 You learn amazingly and try new things, so credit yourself my friend!
Also that's awesome, you should also try Copic markers, apparently they're kinda like water colour but as a marker.