Hi there i suspect i might have giardia from my puppies that tested positive for giardia at the vet, and now im afraid i have given it to my 1 year old niece who now has a runny tummy as well, is there any treatment that is both safe for her and me?

Sure: There are absolutely treatments for humans for Giardia. But I would make absolutely sure that you are treating the correct disease. Get stool samples checked for Giardia before taking any medication. It's just as likely you have a viral illness, so you need to be sure. It's easy to find out, so go ahead and take advantage of the testing and then treat appropriately.