my tortie cat is deathly scared of everything

i have a 2 year old female unspayed tortie and she is so afraid of me and my husband and it's been two years. she doesn't come out, she hides under our bed probably 22-23 hours a day unless she's eating/drinking and occasionally playing with my other cat.
if i make one step toward her, she bolts.

if anyone's experienced a cat like this, were you able to do something to help them and to get them to come out of their shell? it breaks my heart.