The main struggle that these "young, white females" have is that they don't have an identity. Typically, a stronger confident woman struggles with votes - Misha B, Kitty Brucknell (anomaly here is Fleur, but she was extremely likeable in other ways). Older ladies do well in the sense that they have lived a hard working life and we are giving them their last chance (Mary Byrne, Sam Bailey) however unless the younger girl has a "quirk" of sorts (Cher Lloyd, Diana Vickers, Janet Devlin), they struggle to get much support in the live shows. The problem with having a musical "lane" (so to speak) like Cher and Diana did is that is doesn't appeal to everybody so they never tend to make the final.
The act I'd liken Louisa to most at present is Rebecca Ferguson. They're carving out a similar "confidence issue" storyline with Louisa (similar to what Rebecca, Leona and Alexandra all had) however Louisa isn't a classic, diva style belter like Leona and Alexandra were - she's more of a soul singer like Rebecca. Either way, Rebecca did well on the show, and if we can see a bit more personality from Louisa (let's face it, there's potential for that with a longer run up to the lives) she could do quite well. It's acts that are a bit vanilla (Lauren Platt, Ella Henderson, Laura White, Lola Saunders) which struggle.