OMG you guys are so negative.
Okay, real pagan here who practices divination and all that shit *sigh*
This sort of precognition (which means foreknowledge) could mean the obvious, mom's about to check out. Our higher selves do throw road signs at us. Frankly I've had two of those (both were with my parents). They never made me feel freaked out/scared/upset. They did make me sad with a sense of resignation.
But you know what, it could be your subconscious pointing out that your mother is not immortal. It might not be this year, the next year, or even ten years from now, but someday she will depart this plane and what you felt could have been tied more into the feeling that you should make more time for her in your life now, because the time is finite.