How do i tell her to back off?

Get the pony's owner to have a word with her and get the tack back as really that is theft... she doesn't own the ponies tack. If the girl starts to get too pushy then just tell her to back off and leave you alone. I'v had to put up with a lot of it on my yard and yes i do kick some people out because they seem to have parents wrapped around there little finger... are quite happy to let everyone else do all the hard work and then they reap in the rewards. Its people like this that tend to ruin a horse quicker than a novice rider would. If all she worries about is jumping higher then take the jumps away lol! If she really is that irresponsible then get who ever is in charge to have a go at her. Does she do all the work for her ponies herself? or has she made some other poor soul put in all the donkey work for her so that she can turn around and tell people she schooled it hereself...? And if she has 4 decent ponies then why does she need another? IF it was my yard i would definatly of kicked her off by now... Or just turn every1 against her lol!!! or when shes riding start shouting random stuff like.... 'sit up', 'keep that lower leg back'.... just to annoy her lol! have fun and tell the woman that owns the pony that you want the tack because this other girl will treat it like rubbish and end up ruining it x