I know many fans have been complaining that this is Cassandra Cain in name only, but while it's a legit complaint, is Cassandra really that big / popular a character ?
Movies always change some things as they are not adapting comics but they are making movies taking inspiration from comics, for example, Wonder Woman's origins were in World War 2 but in the movie it was changed to WW1.
Flash Thompson in Spider-Man Homecoming was not accurate representation of Flash Thomson in Spider-Man comics and in Sam Raimi's Spider-Man movies, they changed Peter Parker's powers to include Organic Web-Shooters. (what ?)
Baron Zemo in CA: CW hardly looked like his comic-book counterpart, and nobody complained. In comics, Hank Pym was the founder member of Avengers but not in MCU movies.