Besides the fact that she's a girl and makes a delightful form of folkpop, Katie Herzig has another little trick she pulls that makes her much most singalongable than the average bear.
She sometimes uses phrases we already know --- musically but more often lyrically --- to give us immediate buy-in.
From her best-known example "Forevermore", which borrows straight from an old nursery rhyme to the opening line of "How the West Was Won" to the string of known phrases in "I Will Follow": "One step forward two steps back / So funny I forgot to laugh". But none of this would work if the music didn't make familiar lines not merely familiar, but newly familiar and newly known and newly beloved.
Listen to a couple songs then get the album. See what I mean.
(Note: YouTube's blocked at work, so this first video's actually a Target ad. Sorry. And the second one's just squiggly lines. Sorry.)