I am frustrated with my fiancee's elderly grandmother. What can I do?

I'm in a long distance relationship with my fiancée, we want to get married but that basically can't happen until her elderly grandmother passes away.

Now what's very frustrating for me is that nobody else in her family will help take care of grandma. My fiancée is expected to do it all and she's trying so hard to hold down a job that she is on the verge of losing because of grandma. She lives with her and is basically her full time caretaker. Grandma is 90, has heart failure, bad asthma, and anxiety. My fiancée also has bad anxiety which doesn't help matters at all. But what gets even worse is that she's doing the best she can to take care of this woman and she's so selfish and inconsiderate, and ungrateful that she's leading my fiancée to a nervous breakdown. Grandma seems to like to threaten her that she'll call the police on her because of "elder abuse" which she is most certainly not guilty of, but this woman will do nothing at all to even help herself. As soon as she wants something, she calls her and she will not stop screaming her name until she finally comes. She can't even turn on her own nebulizer...or at least until she's mad at my fiancée and then she can do it on her own. But even in the middle of the night she keeps screaming for her and for stupid things like taking her pills and whatnot.

But it makes me even more frustrated when it seems to cut in on our relationship. We have a set time that we can talk to each other at night even on Skype or IRC and it seems as soon as we're on Skype, then grandma calls her every 5 minutes and she's running for her. I'm getting really upset over it because grandma claims my fiancée doesn't need a life and that all she has to do is take care of her. She also guilts her by crying and whining that she took care of her when she was a little girl and practically gave up her life for her and now she expects the same out of her. She's a master at manipulation and because my fiancée has such bad anxiety, she just gives in and gives her what she wants to make her stop instead of putting her foot down, but then she comes to me and complains and cries about the situation. But it truly seems like she's putting her elderly grandma over me and even though I understand grandma needs care, some of this stuff is so unnecessary and unrealistic for her to expect. She even wants my fiancée to lift her into bed and she's a small girl and often complains about being in pain or getting hurt because of having to do this.

I just don't know what to do. Because we live several states away, it's very hard for me to take off work and go over there to do anything unless it's planned in advance or it's a dire emergency. Part of me feels like I really need to be there because she literally has nobody else to support her but then another part of me is getting really impatient with the whole thing and is telling me I should move on. I don't want to do this because I truly love my fiancée and I know grandma won't live forever but at this point in the game, she's just merely existing enough to be a big barrier for us to be together as my fiancée wants to move out of the city she lives in to live with me where I am. I don't know if I should just stick it out and keep supporting her and if I do, what kind of advice can I give her to help make caring for this woman easier so that we can have more time together because as it stands right now, most of the time she's so worn out, frustrated, tired, and exhausted, that we don't really have much of a relationship. The problem with grandma though is she thinks she's the only person on Earth and even when she's in the hospital for something, she expects the nurses and doctors to come right away when she calls and she was even complaining that it took a nurse 20 minutes to come back and check on her so it's obvious she's very selfish and demanding, and she's not afraid to speak her mind either. Any advice would be most greatly appreciated.