Spoiled daughter? Sorry so long!!

So I have a sweet heart of a daughter! She is the MOST caring little 8yr old ever! To the point she gets pulled out of class a couple times a week so she can help with the "Special Needs" kids! BUT, I feel that she is becoming very spoiled or maybe selfish. I hate to say that but I feel it's getting out of hand. Like we were supposed to go to a party Sunday night. But I got a call from my mom saying she's having a little trouble breathing, and she may need to go to the doctor. So I told my daughter that we can't go because I need to take care of NaNa. She says ok, but texts my husband to ask why my sister can't bring her instead! Or the other day her grandpa said he MAY take her out to lunch, but he will call to let me know. So my daughter texts me at 7am wondering if grandpa called! We are not rich by any means so she dosent get whatever she wants, so I don't know how this me attitude came from! So I had a talk with her and explained what being selfish met, and how her behavior is making me and dad feel. Well being her sensitive self, she broke down crying saying she won't do it again. OK well today grandpa took them out to lunch, and after took them to best buy to recycle old cell phones. And she got upset because she wanted to keep them, and grandpa said no, and they need to be recycled. So she comes home all mad saying that Grandpa is mean!! I immediately explained to her again about being selfish and I took away her favorite toy (her iPod). So I'm just looking for advice if anyone here is going through the same thing, or if anyone has any tips! Thanks in advance!!