Starlynn,
you haven't got it yet!! To get information much less have any real hope of getting actual help you have to give/provide information. If I asked you to help me with my daughter who was constantly becoming hysterical, do you think you'd have any idea of what help/advice to give based on that??
You say she's not overweight, but that she doesn't eat healthy & she's very stressed, but that's all. You say you know it's a heart problem you just don't know what. Well if your mum has been diagnosed (actually testewd by a dr & told she has a heart problem) then she (even if she may not have told you) should have or be able to get a fair idea of what the problem is.
You don't indicate her age, or why she's stressed (is it her health or a whole pile of other stuff or both)? How can you or she know that overall she's in fair health?? Plenty of apparently healthy people drop dead every day while plenty of supposedly or really seriously ill people live for years.
If your mum has actually been diagnosed then she can find out a fair bit of detail as to what exactly is wrong & that would help her & you & anyone else help her. If she hasn't been diagnosed, stop assuming she has heart trouble just because it runs in her family. I know families where serious heart trouble runs rampant but not everyone gets it. My own husband is from a family where men rarely survive past 50 (his brother turns 50 this year & he in 5 years time) he smokes, is overweight & out of condition as well as seriously stressed with a stressful job. But none of us spend (or rather waste) our time worrying after all he could be killed in a car accident tomorrow to, but i'm not planning or worrying about that either, after all both he & his brother may be the exceptions - so might your mum, regardless of her symptoms.
Given her symptoms she should improve her diet, do some gentle exercise & realxation/yoga/pilates or similar to destress.
Or if you don't want to answer questions like has she actually been diagnosed or are you all just sasuming then try
www.Lef.Org it's site which sells stuff but also provides lots of free info given various problems - although they too are stupid & want to know what is wrong before you can get help as to what to do.