Elderly Maltese With Heart Murmur?

I have a 14 1/2 year old female maltese, spayed at 6 months, all her vet work is up to date, she has been a loved companion all of her life. She has always had a bad heart murmur, she's been on medication to help with that for the last year, recently had some bad teeth removed and I realize she is nearing the end of a long life. Considering she has always had the heart problem I am surprised she has lived this long. I have made up my mind that as long as she has some interest in food and does not appear to be in pain, I will keep her with me, but when she quits eating and appears ready to give up I will have her put to sleep, but I am asking anyone with veterinary experience, is there anything else I should do for her? She sleeps more, her breathing is sometimes labored, she hates visits to the groomer and obviously the vet. She is not overweight and never has been and can be finicky about eating until I break out the "people food". Any INFORMED suggestions would be appreciated.