Multiple realities
(covers information from several alternate timelines)

Ensign Patricia F. O'Malley was a Starfleet officer who graduated from Starfleet Academy in 2149 and earned a Master of Astronautics from Starfleet Academy on 1 June 2153.

The year is from the description for a Starfleet Academy Graduation Certificate put up for auction at It's A Wrap! sale and auction. [1]
From the Star Trek Encyclopedia (4th ed., vol. 2, p. 96), "We should note that the Starfleet Academy diploma itself was a mistake. The academy's logo establishes that the college was founded in 2161, which is seven years after "Storm Front, Part II", set in 2154. "Observer Effect" (ENT) suggests that prior to the establishment of the academy, cadets attended the Starfleet Training Center, so the diploma probably should have been from the training center."

She served aboard Enterprise NX-01 during its mission in the Delphic Expanse in 2154. In that year, O'Malley was one of a number of Enterprise crewmembers killed in battle with the Xindi; she was only 26 years old.

Later that year, after Enterprise had traveled back in time to the year 1944 of an alternate timeline, Captain Archer allowed Alicia Travers, a native of the time period, to stay in O'Malley's quarters during her brief stay aboard the ship. (ENT: "Storm Front, Part II")

Neither O'Malley's first name nor her middle initial were stated in the final draft script of "Storm Front, Part II".
Patricia F. O'Malley was seen only in a photograph, in which she was portrayed by Amanda Pooley, who was an assistant accountant on the Star Trek: Enterprise production team. (Star Trek Encyclopedia (4th ed., vol. 2, p. 96))