Snoopy, I don't claim to be a psychic or medium at all. However, I do occasionally get "glimpses" of things. I would suggest trying very casually, like in the case of your aunt, to mention "hey, how have you been feeling lately?" In the South, we call this "fishin'" for information.
If she doesn't take the bait, mention something like "You know, I've been feeling a little puny myself lately. I've thought about going to the doctor to get him to check my heart..." Hopefully, this will at least make something stick in her mind, if not open up an opportunity for a conversation.
Unless you know someone very well, or know that they are receptive to something like that, I would, myself, probably heed Mom's advice. However, I don't think it would hurt to drop casual hints, especially if you feel it is something important.
I've read that people with this gift eventually learn to "filter" the information they receive so it isn't a 24/7 type of thing. It sounds as though your abilities are really opening up! =)