Well, it seems like hiding it in food is not an option for her. Maybe the oil trick would do it though? A little bit of canola oil, or maybe even bacon grease, break the pill into it and mix it on the food?

I would also suggest trying the "piller"-it's worked for me with difficult dogs before.

But failing all that-if possible, pay extra for the liquid antibiotics? Is she on cephalexin? Both cephalexin and clavamox have a liquid suspension form...you won't have to pill her, just get her mouth open enough to stick the syringe in. It does cost more-maybe $30 US a bottle? And you would probably need 2-3 bottles, but you could probably return your pills and pay the difference. Honestly I think that is the best option if it is WW3 trying to pill her.