Yeah I think she was just looking to Take That for an example and thought if she was the first one of a massively successfull group to go solo then she was guranteed to be the breakout star
pretty much. it's kind of know she can't dance and found it difficult being on tour as well. i imagine that had influence on her decision as she left before the Spiceworld tour went to the US.
she basically said in the last segment of it that her aime was for a solo career but she wanted to share that success with the girls by being with the band lmao.