Annie is a 900 series S.H.I.E.L.D. Life Model Decoy who was over-coded by M.O.D.O.K. during Fall Of The Hulks, and later reprogrammed as a Gamma Base LMD by Bruce Banner. As a Gamma Base LMD, she has emotions and cares for other beings, including other LMD's, displays individuality, is capable of friendship, requires sustenance to survive, as well as enjoys it, and is granted with the capacity for death. She cares greatly for Thunderbolt Ross, and considers him her friend, as Ross does in turn to her, as he seems to recognize LMD's as lifeforms, and has saved her life from time to time, endangering his own in the process.
Annie by herself is pretty average in comparison to other high level cyborgs and robotics seen in the Marvel Universe (case examples being Ultron and the Sentinels). Despite this, she is a very loyal friend and companion to the Red Hulk, and is the first one to actually break through the tough mental exterior of the former soldier and , essentially, help him learn to cope with his new monstrous form and how to behave more like a human.
Through recent story-arcs, it appears their relationship is going beyond simple friendship, with Thaddeus Ross revealing his past to her along with the home he grew up in and sharing a blanket with her when staying overnight in the desert.
Major Story Arc
Hulk of Arabia
Lower Manitoba Province Canada: Just after Red Hulk finishes fighting General Fortean, Annie calls him back to the truck. She informs him that Fortean received a message about the death of former Colonel Will Krugauer, but doesn't feel this involves the Red Hulk or Ross. Ross disagrees and takes off for Qatar, forcing Annie to call Steve Rodgers and informing him Ross may have gone rouge.
Red Sky at Morning
Gamma Base: Red She-Hulk visits the base, unannounced and tries to destroy Annie but Red Hulk arrives in time to save her and fights his daughter to a stand still, to which Ted She-Hulk leaps away. Annie wishes Ross and Betty could just talk it out but Ross tells her it will never happen. Annie then informs Ross they have a lead on Zero/One and that she will be joining him on the next mission.
Pacific Ocean: While Red Hulk and Machine Man are preoccupied Annie goes below deck of the Gamma Base boat to talk to Red She-hulk who has stowed away. Annie tries to talk to her and convince her to talk to her father, but is interrupted when Machine Man locates Zero/One's man made island.
Annie monitors Red Hulk and Machine Man's battle with Zero/One and her monsters. She is relieved when Red She-hulk goes to help. Annie watches the battle from the safety of the boat while the Ross family is able to defeat Zero/One.
South Pacific: Annie is there when Red Hulk meets the Eternals. She tries to act like the voice of reason to little effect.
Somewhere in the Desert: Ross awakens from a nightmare sleeping next to Annie.
Gamma Base 0900 Hours: Annie debriefs Ross and Machine Man, on their latest intel on Zero/One. Annie has come to the conclusion that Zero/One has phased her homemade island out of phase, thus making it impossible to track. So goes on to debrief Ross on the information they have on Black Fog and his latest killing spree. This is when Machine Man is possessed and tries to kill Ross and Annie. Ross is able to change into the Red Hulk and protect Annie from the possessed Machine Man long enough for Machine Man to regain control of his systems.