she loves to sit at a park and read. I do not want to get a dedicated e-reader
This is going to be frustrating with the vast majority of tablets, as there is too much glare to make them great for reading under the sun. When it comes to outdoor reading e-ink is incredible.
I have an original nook, a nook Color, and thanks to Google a Samsung Galaxy Tab 10.1.
The original nook was a bit of a crazy experiment (those dual screens) but the e-ink is great for reading and nothing else. The new nook looks to be getting some pretty glowing reviews, and it's been rooted, but I haven't read much about the experience beyond books.
I got the nook Color only because of the rooting community, and a bit of jealousy after getting my mother one for Christmas. She likes it but she's only using it for reading. I liked it as my first tablet, but since I still wanted to use the stock ROM there were quite a few quirks in using it that way. If you root it and put Cyanogenmod and the nook app on it, you probably end up with a better experience, but you lose some of the stock features (kids books and until recently magazines).
In either case since you want to get her something that's a bit more of a laptop replacement I cannot suggest any of them; though I would recommended you forget the dream of consolidating the two and get her a dedicated e-book reader.
I was fortunate enough to attend Google IO this year where they gave everyone a special edition Galaxy Tab 10.1. It's an impressive device and has certainly taken over all my after-work computer duties (something the nook Color couldn't quite achieve). It's got front and rear cameras, stereo speakers, and Honeycomb 3.0 - the retail version has 3.1 but we haven't see an update yet. The display looks fantastic, the weight is light enough to not be annoying, the 10.1 size makes it a little bigger than I'd like for carrying (the 7" nook Color is more travel-ready) but the extra real estate is welcome when browsing the web. It works fine for reading inside, but I tend to prefer the nook - both for the e-ink and there's fewer distractions ("One more chapter? Oh look I've got mail... time for some Angry Birds!")
It must have a USB port (full sized + mini-usb would be a plus) and hdmi output would be a nice to have.
Unfortunately, for Samsung to get it as light and thin as they did meant sacrificing all USB/HDMI ports for a non-standard PDMI-like connector and no SD card slots. The fact that Google is touting USB host support in 3.1 and then gave developers a tablet with no USB ports is disappointing to say the least. That said there are adapters available to go from their connector to USB and HDMI, if you're open to going that route.
A number of other attendees have noted some issues with the screen separating from the device and indeed one of the corners on mine shows a little of this. It's not bothersome (yet) but hopefully it's something they fixed in the retail version.
Since I got the Galaxy Tab I've kind of stopped paying attention to the horde of Android tablets being released, but one of my co-workers is pretty much sold on the Thrive. It certainly looks to be a pretty solid device if you aren't after something sleek and sexy. It's also one of the heavier tablets out there, though Engadget's recent hands-on stated that it felt good in their hands and seemed lighter than they expected. The actual pictures of it were much better than Toshiba's mockups as well.
It might also be worth looking at the ASUS Transformer, I know it was released with 3.0, but it's yet another option.
To be perfectly honest though, I think I'd try to hold off on buying any tablet until Fall or 2012 - it's a young market with a ton of competitors so I expect a lot of quick improvements and some price drops in the near future. Also, Apple is driving this market at the moment, so it might even make sense to see what they do with the iPad 3 since they'll likely be the ones pushing the goal markers for another year (or more) while the Android manufacturers catch up/flood the market.