I prefer Alexandra. Alexandria is lovely too, though. If you're looking for variants on Alexandra there's also Alessandra and Alejandra? Or Alexis, Alexa and Alexia for shorter versions?
Middle name ideas:
Anne, Beth, Claire, Faith, Faye, Fleur, Fallon, Grace, Giselle, Hope, Jade, Jane, Joan, Kate, Lucy, Lauren, Leanne, Megan, Mirren, Maeve, Mabel, Niamh, Nicole, Nancy, Nell, Olive, Paige, Phoebe, Poppy, Quinn, Rose, Rachel, Ruby, Seren, Sadie, Susan, Tamsin, Tess, Tegan, Willow, Xanthe, Yasmin, Yvette, Zoe