I think this is just a made up rumor. The characters that they are saying she is in talks to play are Blink and Boom-Boom both of which are mutants,and both belong to 20th Century Fox, And the studio that makes the Avengers movies don't have rights to those two characters. the only two characters Marvel Studios and 20th Century Fox share are Quicksilver in the Scarlet Witch.so unless these two studios made deals within the last 3 days, there is no way B could play those characters in Avengers movie