Alexia Ashford first appears in Resident Evil: Code Veronica. She was heir to one of the founding families of the Umbrella Corporation, and a brilliant scientist to boot. The reason for the latter was less than coincidental, as both she and her twin brother were the result of a genetic experiement by her "father" to create the smartest possible offspring to carry on the family line. Relieved that she shared no genetic ties to her failure of a father, she choose to use him as a test subject for her creation: the T-Veronica virus.
The test was a failure, and Alexia surmised that if she was to claim the virus' power as her own, she would need to enter suspended animation for several years so that her body could slowly adapt to the virus. Entrusting her brother to handle her affairs in the meanwhile, Alexia injected herself with the T-Veronica virus and went to sleep for fifteen years. She awoke to find her brother dying in her arms while his killers escaped in a snowmobile. Claire and Steve were incapacitated and returned to the base by a telepathically controlled tentacle, while Alexia waited for more guests to arrive.
Both Chris (looking for his sister), and Wesker (looking for a sample of the T-veronica virus) would appear at the base, and after Alexia began her first transformation before them, their combined ability only ended up stunning her. After Chris succeeded in arming the base's self destruct sequence Alexia reappeared and forced a confrontation. After several successive mutations Chris destroyed her utterly with an energy cannon, and any remaining trace of her or her brood were vaporized with the base's detonation.
The range of Alexia's abilities just after awakening are unknown, although it is suggested that she has some amount of control over the T-virus mutations in the base, such as the tentacles and a giant spider. In her first mutation her skin turns grey and veiny growths replace her hair and appear over her limbs. She gains a limited resistance to firearms in this form, and her blood becomes flamable, bursting into flames only seconds after being exposed to the air. She can also projectile vomit an acidic green ichor.
Repeated damage to this form will cause her to mutate further, becoming massively pregnant and immobile. In this form she will constantly release small beete-like creatures from three orifices on her forso, as well as shoot out long whip-like tentacles from those same orifices. After this form has sustained enough damage Alexia's body seperates, and she takes to the air with her four dragonfly wings.
While Alexia's body is shown to have survived her first encounter with Chris, she first appears as a headless, unmutated body deposited by a tentacle in their final encounter. The body is then rapidly mutated into Alexia's first form, now complete with head. What this says about the range of Alexia's ability to replicate bodies is never expanded upon.