lonely vs. alone

Is there really a difference? And if so, how different is the difference?
1.A person can feel alone and lonely.
2.They are both descriptive.
3.They both sound terrible.
When i hear or see either word, i think of an old lady in a huge house with a bunch of cats and no friends. I know of this lady who is in her 80's. She didn't get married until she was in her late 50's and has no children. She was an only child and of course her parents are dead. She lives in a nursing home and has no family to come and visit. She has friends who stop in every once in a while. But for the most part, she is alone and i would be willing to bet, very lonely.
I get confused because, if i am happy this way now, and don't marry until much later, and end up like this lady, how happy will i be later?
I say all of this as if there are prospects in my life. Some handsome fella waiting in the wings, but there is none. The bottom line is, all of this is out of my control at the current moment. There is no guy, there is no hope of anyone, and i'm not entirely sure that i want there to be.
But i think of myself padding around my mother's house in my pj's with my dog, and i feel like i will be that way forever. Sometimes that makes me happy, sometimes it doesn't.....
I wonder if that lady is grateful for her 16 or so years with her husband before he died, or does she wish that it had happened sooner?
I think the difference is, i can deal with being alone for a long time, but i certainly don't want to be lonely forever....