AutoTrader helped The Overly Attached Girlfriend find her car, her way.
She could totally start her car search on her boyfriend's computer (not that she was reading through his emails or anything), then save and pick it back up on her tablet (before he realizes she knows his password).
And by adding new cars she might like to her saved search, and sending alerts when prices drop, AutoTrader keeps working for her while she's busy being a good girlfriend (sewing her name on his clothes, in case he forgets he's taken