Help, Tuna's heart is too big!

My beloved Tunafish is just over a year old and was seemingly happy and healthy until this week. Her overly affectionate self who is always eager to greet anyone at the door for chin rubs became severely withdrawn. Her typical exuberance for food became a complete lack of appetite. Knowing this total behavior reversal was indicative of a larger issue, I took her to the vet. Initial xrays yielded ambiguous results. We took her home and monitored her for the night and the next day made the decision to take her to the ER at Angell Memorial Hospital after her breathing became shallow. A second round of chest Xrays reveled that Tuna has an enlarged heart. Because of her age she was likely born with a heart condition (just like her momma). Her enlarged heart is causing a fluid buildup around her heart and lungs which is likely the cause of her symptoms. However doctors are still stumped on a diagnosis because her symptoms overlap and don't clearly point to one clear culprit. Until we can get her properly diagnosed we are unable to treat her and get her better which means further tests are required. We've put $2,000 into her treatment so far but because of the acute nature of our situation we are asking for help to get Tuna the care she needs so she can lead a long and happy life. If donations exceed the cost of her care they will be given to Angell Memorial Hospital to help continue their dedication and compassion to bettering animal lives and to show our gratitude for the outstanding care we've received. Her Moms and her Dad miss her very much. (And so do her sisters Boo and Mo.) Our sweet girl is the hit of the hospital because of how much love she has to give to everyone she meets, she truly has a big heart in more ways than one, but... we want her home, any contribution means the world to us. Thank you so much.