What a lovely caring friend you are Stanlaw. All you can do is to continue to allow her to talk to you and let her get through this awful period of her life. I feel for her very deeply as much of what you describe of her life mimics my own. I have been through a very similar bad patch this year and have relied on about 4 close friends to have the patience to listen to me and not judge. My OH has been supportive best he can, but there is nothing like close girlfriends. I found that by hearing myself talk about my situation I came to understand my own thought processes and feelings and started to come to terms with the situation and move gradually into a happier place. But it is sometimes 2 steps forward 1 step back, but still progress.
Your friend may well find your own happy life circumstances difficult - I know I tended to cut myself off from friends and family who seemed to have the perfect life purely because it only exaggerated my own rotten circumstances (not n cessation of my own making). She may well be feeling a burden on you as a friend right now. The suggestion of offering to spend some time with her, if at all possible, could be a god send to her as she possibly is reluctant to ask.
Perhaps she is feeling guilty because there is much relief in no longer having to look after elderly parents, but at the same time huge grief for the loss of the relationship which had been her focus for so long and a massive hole that needs to be filled. We have words widow/widower when a spouse passes away, but we don't have words for having lost your parents that is indicative of the importance they held in your life - orphan doesn't really fit the bill!
Be assured you are helping by being patient and willing to listen and discuss. Not much fun for you I know, but she needs you more than ever now. Remember loneliness is still very hard to admit as it implies self pity, but can simply be due to circumstances out of your control and an indication of knowing what to do next for the best.
Good luck and keep doing what you are doing. x