I think that this movie is so highly anticipated that every person who is casted is being speculated to being such a critical role simply because of how much we can't wait for this movie to come out. So I doubt that this young actress is going to be such a key character like most are predicting. She'l be like that little kid from Batman Begins that Rachel saves at most.
:batface: THERE WILL BE NO BATGIRL OR CAT-WOMAN SIDEKICK OK !!!!!!!!!!!?????????????
If it is confirmed the most interesting thing for me is that this is an indication that Nolan bases his inspiration for TDKR again on "Year One" and "The Long Halloween" which makes perfect sense for me story- and characterwise!