enlarged Atrium

My mum (83) has just been told that she has an enlarged atrium.  She is very breathless all the time, and also has high blood pressure.  She is under a lot of stress and lost her partner of 62 years, just over 1 year ago.
I have many questions and would appreciate any answers.
1) Can the atrium return to normal, or is it a permanent thing?
2) If we reduce her stress levels, would this help her condition?
3) Would it be safe for her to fly (1 hour flight) so that I could bring her to me to care for her?
4) Is this ONLY related to her blood pressure, or could she have the enlarged atrium from other problems.
5) she has also had some build up of fluid, is that also related?

Any suggestions as to how I can help her... I feel helpless.
Thanks,
Nicky