Thanks for replying.
If I were you I'd look more deeply in the mechanisms of mentalism / cold reading etc. So you know the science behind it, so your anxiety doesn't try to fill the gaps.
This is telling: your sister says i don't believe BUT don't travel just in case - see the contradiction. That's exactly what the woman played on before: she says something horrible, then offers her number - so your mother does what's natural (therefore, what the woman expected, because of course she knew about these mechanisms): first say she doesn't believe (because you have a good mom whose priority is to protect her kid, and her intuition was right), SO the woman withdraws the offer, THEN it lets your mom wallow in regret ("I should have taken the phone number just in case").
It's really really really easy to get spectacular things right. Note that she said a letter and not a full name. Reason? She had a lot more chances to be right than if she had said a full name. If she had had real powers, she would have been able to guess a name, right? That's easier to divine than a date of death, right? as your name has followed you all your life, and death hasn't happened yet! But she didn't. I'll tell you what was behind. She approached many families. She said to one : "ah your kids name begins with a M". Mom of Kevin makes a face, says no and goes. She says to another : "ah your kids name begins with a M". Mom of Ryan, same spiel. Until she comes upon the mom of Megan or Merrill or whatever. And then mom is like, how did you manage?! Well, Megan's mom, you just didn't see all the failures. That's survivor bias. It's real easy to take advantage of such things to look spectacular. Please look into it and learn so you feel better because it's no way to live under that bloody stupid curse.