This is a common story, so forgive me if I don't go into lengthy detail again.
Oh, first of all, welcome to the forum! where are my manners?
Your mare is displaying behavior called "barn sourness" you can learn more about what other persons on this forum do to deal with this very common issue by doing a search for "barn sour".
As for the young fellow with spurs getting results, well , your horse knows that he can MAKE her do what he wants he to. He has the self confidence that unfortunately, you don't yet have. Horses can read this like radar. They know if the human on them or leading them has the confidence and authority to demand and get what they demand . Of course, we are not always demanding when we ride or work with horses. Optimially, we are asking them to move this way or that, to stop, to go faster/slower and on and on. But we have to be recogonized by the horse as someone who is worthy of obeying.
You may be new to horses? you will need to work on espablishing a position of leadership and strengthening it to the point where even though your horse has a powerful emotional draw (and make no mistake, horses are totally emotional creatures), YOU can make her go where you want.
I think more exploration here, more reading and bringing a trainer in to help you with these issues will be the best for you. IT's very hard to do this on your own.
Good luck, and again, welcome.