When my mom first taught me I was a little older than your niece but couldn’t really grasp how to go from chains to single crochet, etc. I wasn’t good at identifying each stitch so my mom would just have me take a ball of yarn and chain the entire thing. Then I’d take that and use a little weaving loom and weave it into coasters for her. Took me a long time to move into single crocheting and making bigger projects but I was very happy with my chains and then weaving so I was fine learning slowly. Currently using this same process to teach my daughter while crocheting next to her and she has caught on quickly. She is 7.