Gilson represented Ireland in the Miss Hawaiian Tropic in 2002 in Oahu and went on to win the title for Europe. Her success secured widespread international exposure, as she appeared in the pages of Cosmopolitan, Marie Claire and Company and Ireland's own VIP . Gilson made two guest appearances in Katherine Lynch's Wonderwomen.
In August 2006, Gilson embarked on a presenting career, appearing as the face of Irish music channel Bubble Hits hosting the news and entertainment show Glenda's Showbiz Gossip. In 2008, she soon found a new home for her celebrity gossip insight and fashion knowledge by joining TV3's Xposé team on a part-time basis before becoming a permanent fixture as of 2009. She appeared as a contestant on the RTÉreality show, Celebrity Bainisteoir.
Gilson and her brother Damien could face jail after consistently refusing to comply with court orders in relation to the liquidation of their car company. Justice Mary Finlay Geoghegan said in May 2011 that Ms Gilson and her brother are “not compliant” with the rules and described the situation as “extremely serious” and “the motion for attachment and committal still stands.” In 2012 Gilson was revealed to be a tax defaulter. On 14 September 2012 she was named on the Revenue list of tax defaulters as having been required to pay €73,000 including interest and penalties.
Gilson is a niece of former Fianna Fáil politician Liam Lawlor, who died in a car accident in Russia in October 2005. She was at one stage involved in a high-profile relationship with Irish rugby captain Brian O'Driscoll. In August 2014, Gilson married Dublin businessman Rob MacNaughton at St Senan’s Church in Kilrush Co. Clare. Gilson and her new husband honeymooned in the USA and Mexico.