Trisha Billings is a character in DEXTER. She is a former classmate of Dexter Morgan, originally sitting behind him in biology class. She later grows up into an attractive young woman who has an interest in Dexter.
Trisha is an attractive blonde in her late 30's (though she appears to be much younger than most at the reunion), displaying a tan complexion with a bright smile. She often uses her body language to detail her interests, most specifically in Dexter's direction. Her body itself is fit and slim for her age, underneath the clothing revealing her as a woman that could easily be in her 20's rather than 30's.
Trisha is, to say the least, a vexing woman. She (like Dexter) arrives at the reunion looking likely better than she ever did in high school and as soon as she spots Dexter, she begins to flirt heavily with him. Her attraction to him is sincere as she has nothing to gain aside from her own pleasure, so much that she continues to play meet and greet with everyone after her encounter with him (and apparently, turns down Joe Walker's advances). She apparently used to be the prom queen back in high school, suggesting she was one of the most popular girls then and would never have anything to do with someone like Dexter.
Little does Dexter realize that this attraction she has is strong enough for her to advance on him (while he's attempting to go lure Joe out for a kill later), walking beside him describing how she has grown fond of him. She reveals that back in high school she used to sit behind him and copy off his work, something that she claims got her through in the end...and she wants to pay him back. She begins kissing him, forcing Dexter into the classroom where she openly drops her dress (revealing that she's wearing nothing but panties) and proceeds to give him oral on one of the tables here. After she finishes, she jumps up happy and perky as ever...putting on her dress as she smiles to Dexter and walks off with purse in hand (not realizing her phone has been lifted for the purpose of Dexter luring Joe into a trap later).