Wow your niece has a lot in common with me! Libra sun, moon and jupiter in 3rd house. With that stellium in the third house i can see she'll probably be very bright. She also has venus in 2nd, virgo same as me and leo rising. Her bday is the same as mine too
do i think theres a chance she'll be famous? The potential can be seen in a lot of charts but it depends on what we choose to do with our skills and the chances we get in life. I think shes too young to tell
I can see why she may be artistic, with the trines there from Sun/Jupiter/Mars to Neptune. Neptune and Venus are both singletons (Venus is the only Earth and Neptune is the only Fixed sign) so that may seem to be a calling associated with arts. I don't know though. I think she may want to go college first with all that energy going to the third house; she's probably a keen learner. Neptune in 6th usually indicates someone who is prone to pick up lots of illnesses such as the flu etc, but I guess if we look at the 6th house only from the job perspective, it could indicate a job working with animals, the arts, healing professions, the psychic realm.. but these are just theories, I haven't actually looked it up. Pluto in 5th house could potentially make someone passionately creative. I also read that the ruler of 10th in the houses play a big role in your profession. Celebrities could have their tenth house rulers in the 5th house, 3rd house or 2nd house, indicating a career associated with creativity, communications, or using their voices (2nd house rules the voice- funnily enough, I've noticed a few singers with their 10th house ruler in the 2nd or 3rd). With her 10th house ruler in 2nd, this supports making money through the profession of her choice, but it can also mean using her voice a lot in her job, a job that requires her to speak up. With Venus in 2nd, making money through arts, beauty or love is supported. Does she have a good singing voice? Since Sun is in the third, her opportunity of fame will come (if it comes at all) through communications and/or the things Libra rules.
Also, if you use astro.com you'll find it's a lot easier to read and it's a bit more detailed. Read what "ASTRO LADY" said about fame on here:
http://www.linda-goodman.com/ubb/Forum1/HTML/009505.html