Just being in the TARDIS wouldn't have done it. It's that she was conceived whilst the TARDIS was travelling through the Time Vortex. It was always the exposure to the energy from the Untempered Schism of Time and Space over a period of living near it for many generations that caused the Time Lords to exist in the first place, beforehand they were just another basic humanoid species and nothing special really! In being conceived within the Time Vortex, and therefore travelling through the stuff that makes up the Untempered Schism, Melody Pond managed to skip several hundred generations of evolution and came out part Time Lord!
MissyMojo- I've heard September but I'm not sure!
Beca :wave: