ChiChi Has ENLARGED HEART

I BOUGHT THE CUTEST CHIHUAHUA  FROM A BACKYARD BREEDER.MY THOUGHTS WHERE ONE LESS THAT HAS TO BE IN A TERRIBLE PLACE.I HIGHLY REGRET IT NOW BECAUSE I GAVE THE WOMAN 350.AND SHE DIDNT DESERVE IT.ON MY FIRST VISIT TO VET AT 8WEEKS I MENTIONED SHE HAD A LITTLE COUGH.WELL SHE HAS AN ENLARGED HEART THAT WAS SOMETHING GENETIC.ANYWAY,SHE HAS BEEN ON HEART MEDICINE FOR 2.1/2 YEARS NOW.
WHAT A STINKER,SHE RUNS US AND RULES OVER MY OTHER DOGS.ANYWAY,I TRY TO CALM HER WHENEVER I CAN BECAUSE BEING A CHI CHI SHE CAN GET VERY AGRESSIVE.I DONOT LET HER THOUGH,AS I WORRY SHE WILL MAKE HER HEART WORSE.
DOES ANYONE HAVE AN IDEA HOW LONG SHE WILL BE ABLE LIVE.SHE HAS REGULAR VISITS TO VET AND HE WON'T ANSWER ME.IS THEIR ANY OLD DOGS WITH BIG HEARTS,LITERALLY?THANKS MADDY

[lindapalm]

Can you google your question, poossible there is a site than give you a good answer?  Also, if you scroll down and click on Ask a Vet on the right side of this page, perhaps they can give you an answer.