Did she have an actual heart attack Legend, or did she think she was, or have chest pain, and then they found a heart murmur? As has been pointed out, murmurs are fairly common. Ditto irregular heartbeats.
Speaking as someone who just went through a heart scare in June...I got the idea that this stuff is scarier than it actually is, if that makes any sense.
Regardless of what happens, they will run her through the battery of tests, up to and including going into her heart with a catheter, which isn't nearly as bad as it sounds. And then, after that's done, they will do even more tests. The tests suck. My grandfather, who had a quadruple bypass six months before I went through my regimen told me that the surgery itself is less annoying and painful than most of the tests were.
Go into an urgent care and say "I have chest pain" everyone. Watch what happens.
Hoping for a speedy recovery for your mom, I am Legend, and hoping you and yours are doing all right. Please keep us posted.