Is something up with my guinea pig?

She's taking a lot of little naps which i've heard is normal and most of the time she become alert after I say anything plus she's only deeply and comfortably asleep (eyes closed foot out) during the day once or twice. One weird thing is that she'll be lying down in her cage then i'll take her out and she'll start pop-corning like crazy and then she'll go to sleep again outside. She's about 2 1/2 pounds and has a really healthy coat. She's responsive and runs to her food bowl whenever I put anything in there (I give her her dry food, hay, fresh water and some veggies in the morning before I leave) and sometimes even stands on two feet or starts climbing the bars. ONe small thing that bugs me is that even though she's pear-shaped and her tummy's pretty chubby her 's kinda bony and I was just wondering why this is...oh and one last thing- she had a friends who died about 5 or six months ago and she seems pretty ok now but sometimes when I have to much to do and can't play with her she looks a little bored and starts sleeping but I don't really want to get her a new friend because she's sorta become adjusted to having the whole cage to herself plus I'm leaving for school in a few years and wouldn't really want to get another baby (especially if they don't like each other) so I was just wondering if anyone had any suggestions for that :)