I'll have a look at the files as soon as I get the chance. If you've already tried and the sound is still too tinny then maybe a compromise would be best, or manually removing the worst of the breaths and replacing with ambience the (very) slow and meticulous way. Another option is once you've removed the other sounds and she ends up tinny, you could try saving that tinny file - and once the extraneous sounds have been removed they won't be in the waveform any more and you can then try equalising to add bass back in - no guarantees that it'll work though!
The main issue as I mentioned before is microphone popping (known as "plosives") whilst recording - you can use a relatively cheap mic and use some tights/pantyhose stretched over a bent clothes-hanger or similar and you'll get arguably better results than an expensive mic without a pop filter. If you really can't mock up a pop filter, recording at an angle to the microphone also reduces pop - put the mic at the side of your face rather than directly in front, so when you breathe out you're not breathing directly into the mic.
And I think you're right, the room also makes a huge difference - computer sounds (fans, disk drives etc.), electric hum from pc/lights/fridge, ambient sound from outside the room (traffic rumble, birds, the occasional plane) and general actor movement (rustling of script, leaning on desk, moving on chair, etc.) The human ear is great at filtering out sounds in reality, but a mic isn't as discerning and picks up everything.
When recording, it's best to record in as small a place as possible - and as far from those noises as possible - maybe enclose the mic in a small box (cardboard box, shoebox or similar) and pin a shirt or a towel to the inside of it and use it as a mini recording booth).
If your mic is plugged to your pc, see if you can block off the area where the sounds are coming from (put a blanket over the pc temporarily with a airing space and AVOID OVERHEATING - and turn down the fan speed if your desktop has fan speed control.
I once worked with a professional voiceover artist on a big corporate job who recorded in the cupboard under his stairs with a load of sheets stuck to the walls to deaden the sound (Harry Potter could have made a decent living as a v/o artist had he stayed at home!)
EDIT: for a good guide on voiceover recording, see http://wiki.librivox.org/index.php/Improve_Your_Recording
EDIT 2: Nope, there's not a lot I could do with the file without it sounding tinny - http://www.mediafire.com/?1ire39p8xzsol9h (from the original file http://www.mediafire.com/download.php?3jeeg12n3gm9mn3) Having said that, on my speakers the version without the popping despite the tinniness is a lot less offensive to the ears than having all the popping.
EDIT 3: Here's the best I could get as a preset without lots of individual tweaking (each time the words pop you can select just that popping sound and manually reduce the gain or use high-pass filter just on that part of the recording, but that's likely to take a ridiculous amount of time with the amount of pops on each recording and the number of recordings you have) - http://www.mediafire.com/?4iw5bi2tlm7m56d. If you're interested, here's the EQ settings exported from Audacity - http://www.mediafire.com/view/?lvibf6071bm827t - you can import this into Audacity in the EQ box if you'd like to use it as a preset for Beatrice. No offense taken if you don't like it!