My thought:
Spoiler:
I have to wonder how this will be explained if she really is alive. She maybe found out that somebody was coming to kill her and she survived the explosion with Tali, but some how hid her presence from the investigators, but left a message for Orly explaining the situation and asking her to take Tali to Tony. That's about the only thing I can come up with, because she would never in a million years leave her daughter otherwise.
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