She sounds so much like my first and third kiddos. I had to force tummy time with both of them as they were so much happier to sit and look at the world around them instead of being on their tummies or backs. If she's happy to sit, then I'd leave her sitting there while you do other things so you're not constantly entertaining her -- but it does sound like you probably need to force the tummy time issue -- not that it seem like there's a problem, but just because if you don't, there may eventually be one, if that makes sense. So, while she's on her tummy/back, I would probably stay close by and entertain her - get down on the floor and play with her so she has the increased tummy time. If she hates it that much, you could always do it in smaller bits a bunch of times a day. I'm sure that once she figures out she can get places and reach things while she's on her tummy, she'll be happier with it.