Did you change out the foot to an embroidery foot? There is a big groove in the bottom of it that allows for more stitches to go under it.
I use a thinner thread to eliminate the bulk the satin stitches make. And last but not least, Maybe the bobbin has been overwound and the thread is not turning right in it. Also, check to make sure the machine is threaded right. I know this has happened to me before.
I hope she gets over her headache soon, that little girl needs to get your groove back!
Edited to say I should have read the whole thread... LOL.