Thats she wasn't invited to both? I don't see a problem or anything strange with that, My dd's communion is coming up and due to space issues I can't have everyone come to the church but they are invited to the party.
Bar and Bat Mitzvah ceremonies are typically held during regular Shabbat services when the Torah is brought out and the weekly portion read. Thus, anyone can attend. DH have attended Shabbat services when a bar or bat mitzvah has been occuring.