Taylor Swift Donatee's Mother Says They Didn't Hear From Taylor Before Donation

Taylor Swift's $100K donation has totally changed a cancer-stricken girl's life ... but, that young girl's mom says it came completely out of nowhere -- 'cause Taylor dropped the dough without ever reaching out to the fam.

We spoke with Katelynn Smoot, whose daughter Lilah was diagnosed with a rare and aggressive form of brain cancer earlier this year, about what the donation means to her and her family ... and, Smoot says it's given the family time to catch their collective breath.

Smoot says her husband was refreshing the GoFundMe one night and noticed the donation ... leaving the couple totally awestruck -- 'cause Taylor never reached out to inform them of the gift.

In fact, Swift still hasn't reached out ... it seems Taylor did something out of the goodness of her heart and simply moved on -- and, Smoot ultimately decided to post about it to highlight how wonderful she is.

Smoot explains she and her husband were discussing their finances mere days before the donation ... trying to figure out how long they could be out of work so they could focus on Lilah before they ran out of money -- but, Swift's donation has totally wiped that concern away.

On top of that, Smoot says Swifites have chipped in now too, alleviating the burden even more ... and, she adds, it feels like their family is wrapped in a warm embrace by the fans. Katelynn -- who is a big Swiftie herself -- previously admitted she nearly named Lilah "Willow" after Taylor's song of the same name.