hi S.;
i would bet that what's happening is a combo of things; first of all, toys probably don't interest her. neither of my children played with toys at all until they were over a year, they just didn't care about them. it's very possible that no toy will interest her. kids don't inherently know how to play with toys anyway, they only know how to explore things. you could try showing her how the toy is meant to be used and see if she follows but what i would do is toss the toys into laundry basket and stash them in the closet for two or three months, then reintroduce them.
secondly, are you going outside? babies that age do like new enviornments. try a grassy park, a clean beach, a playground, a play center with a baby area. anywhere that she can crawl around freely and look at stuff. as another mother pointed out, it sounds like she is very bored and needs a change. and please don't prevent her from getting 'dirty,' babies love to be dirty, and healthy babies will not get sick from normal playground or fun area dirt. of course don't let her eat it, but don't panic if she sneaks some; my 16 month old stuffs fistfulls of sand into her mouth every time we go to the beach, and would eat dirt by the spoonful at the playground if i did't stop her.
also, perhaps your baby is very very smart and needs some kinds of stimulation that are more compelling. have you tried DVDs like Baby Einstein or Teletubbies? my 3 yr old boy didn't care for TV till he hit about 2, but my daughter has loved TV since she was about 8 months and she would talk to it and get excited about it and point to it and laugh. some kids get a lot out of it. it's not a bad thing, it can be a great thing, so long as you don't make it a substitute for your attention. also, try music, and try reading to her. and how about finger painting? i put my daughter in her high chair at the table, cover the table with a plastic table cloth, put her art smock on and let her go crazy with the finger paint; she does eat it but i get the non toxic and it has been fine.
as another mom suggested, but i would say AFTER you try these things, you don't see a new interest, then i would take her to the doctor. look at her for other ways in which she might be despondent; is she a bit yellow? very tired? not gaining weight? if so then she could be having a nutrition problem of some kind. also, what are you feeding her in general? if its only baby food, start trying exciting solid food like zesty fruits, crunchy vegetable, ice pops, chewey bread. that could wake her up and renew her interest in all kinds of sensory things.
good luck!
J.