Little has been revealed of Sally Blevins' past. It is known that her power first manifested after she was abused by her stepfather. Her mother Matilda is deceased and the current whereabouts of her step father is unknown. She ended up a runaway, living on, or rather under, the streets with the Morlocks, a group of homeless mutants. Most Morlocks voluntarily (or, in some cases, involuntarily) took on inhuman appearances at the hands of the Morlock facial sculptor, Masque. Sally's force field protected her from Masque's power, allowing her to maintain her normal appearance, leading to resentment from some Morlocks. At one point, Skids encountered Quill, who was being pursued by the Freedom Force (government-chartered mutant enforcers composed of former members of the Brotherhood of Evil Mutants) and a mob of mutant-hating humans. Maxwell had accidentally injured a woman with his quills and was wanted by the U.S Government. Skids' force field allowed the two to easily escape, but were eventually overtaken by the Freedom Force on the edge of Central Park.
Before the evil mutants could take them in, a mob of humans attacked the Freedom Force. In the confusion, Skids and Quill escaped. Skids tried to get Maxwell to the safety of the underground home of the Morlocks, but the Freedom Force caught up with them again, this time in the sewers beneath New York. The Force member Blob was pounding Quill into the sewer wall when the mutant hero team X-Factor arrived. After a brief skirmish, Freedom Force retreated.
With X-Factor's mentorship, Skids and Quill began to learn more about their powers, and were the first of several X-Factor protegees transferred to the Xavier Institute. They shared other adventures alongside the rest of the students, at one point calling themselves the X-Terminators.
Source: http://marvel.wikia.com/Sally_Blevins_%28Earth-616%29
http://www.comicvine.com/skids/4005-3194/
http://www.angelfire.com/comics/benriely/skids.html