Help with my dog again?

OK here is the drill I have had my largest dog named Missy for about 6 or 7 years. I found her as a stray and did not want to send her to the pound. The problem is that she will not get in the bath tub, she use to love baths, is it because of her age she has a stubborn strike I wish she would come out of this phase and get back to her fun loving state but it seems that all she wants to do is lay around and do nothing (LOL). At the moment I can not afford to pay anyone to give her a bath so I was wondering what do I do. I tried the whole treat thing in the bathroom, giving her treats did managed to get her in the bathroom just not in the tub. I have also given her one on the hose but she gets very angry when I do that. But all and all she does listen when I tell her to sit, stay, you know basic commands, but when it comes to bath time it's another story. Can someone help me out give me as many pointers so that she can get a bath like normal dogs (LOL). By the way she is a pit bull mix, I love the breed!