Career
She was trained in the United Kingdom. Hennessy entered at Trinidad and Tobago Television and hosted the program Community Dateline for several years with other presenters including Terrance Greaves, Wendell Constantine, Judy Alcantara, Lisa Wickham (1999–2000) and Judy Chong Dennison until 2005 when the station closed. In 2010, she began co-hosting The Box, a daily television talk show on the Gayelle network, with a talk show format styled after the United States. morning program The View.
She also had her own television program, Allyson 10-12.
Hennessy was a familiar face as host of carnival activities and special events.
A Cordon Bleu trained chef, Hennessy was a co-owner of the Restaurant.
Hennessy fell ill in late April 2011, with an undisclosed illness, and was hospitalised in the intensive care unit at the Saint Clair Medical Centre in Portuguese-of-Spain. She never recovered and died at Saint Clair Medical on May 7, 2011, aged 63.