It took Old Blues only three minutes to catch the United defence napping and they scored from a tight angle.
United responded well and were level on 10 minutes when an excellent cross from Alice Bennett was met by Keltie McManus, who rocketed a shot past the Old Blues goal keeper.
Old Blues dominated Untied for the remainder of the first half, going into the break 4-1 up.
United scored their second on 54 minutes through Halee Smith, but a lack of composure in front of goal resulted in an Old Blues victory.
United suffered a double blow during the game, with inform goalkeeper Amanda Wilshier having to leave the field early in the first half with a shoulder injury.
However, it is hoped Wilshier will recover in time for this weekend's big match up against Cambridge.