So this is a bit of a vent, sorry. Our RSVPs were due back on 9/8 - over a week ago, and we're still waiting to hear from some guests. We've contacted everyone we hadn't gotten a response from, and most of them apologized and answered us. But I have a couple of extended family members who apparently don't believe that deadlines apply to them. We have asked them if they're coming, and they've just said they're thinking about it, pretty much. My aunt says she's looking for a cheap enough flight out here but really wants to come, and my uncle (different family) just said he's undecided.
I'm going to call the uncle today and hopefully he will have decided by now, but I'm wondering if there's anything I can do about my aunt. We asked her to let us know by this weekend, and she replied with a sad story about why she can't afford the tickets but how much she wants to come. So, I sent her flight prices that I found, and told her that in my experience she probably won't find anything cheaper (which I think is true, unless maybe you catch some last-minute sale?). The flights were under $200, so I hoped that between that and my telling her it wouldn't get cheaper, she would make a decision based on that, but she just responded that she would keep checking. That was last night, so I presume I'm not getting an answer by this weekend... She tried to excuse it at one point by saying we don't have to feed her if she does come, but I'm not going to do that.
Is there anything I can do about this? I just want to call her up and tell her she's being rude, but something tells me I would regret that.

Should I just seat her somewhere and put her in the guest count and forget it? Is this piece of my sanity worth that $25 dinner going uneaten? Can I just not count her since there should be more than enough food even if she does come? Does anyone with a magical way with words have a suggestion of something I can say to her?
Wow, sorry again for the length.