Why does my dogs vulva swell very big when she is in heat?

Ok some mite not belive me and if you don't please don't waist your tyme answering because I'm not interested...ok I have a 3 year old pit bull and she's been in heat about three times and eveytime she goes into heat this pink small ball comes out of her vagina and it keeps growin untill its about the size of a tennis ball I wanted to see if anyone can tell me how can I make this go away...the vet wants 92.00 to see her and what ever else it cost to fix it but I don't wanna go to the vet if its not that serious..some please give me some goods answers I was told that she's backed up and I should put my finger inside to release the liquids is this true.