The blonde TV host was spotted backstage alongside RTE's Dan and Becs, actress Holly White, and Colin Morgan and Katie McGrath, stars of BBC drama Merlin.
Despite the rain, with more showers predicted for today, music fans were in buoyant form as they rocked out on the opening night of the festival in Punchestown.
International pop stars The Script announced details of a major Irish tour for August and September, starting with a five-night residency at the Olympia.
Lead singer Danny O'Donoghue said: "We've been around the world, but one thing we've perhaps not done is really give something back to our Irish fans.
"A lot of bands come and do Ireland as a warm up gig for the rest of Europe, whereas we use our European gigs as a warm up for our Irish set. It will be great to come home."
Brit pop maestros Blur paid an emotional tribute on the main stage to the Irishman who championed them in their early days.
Music journalist Leo Finlay has been credited with introducing the band to the world in the late 80s.
Lead singer Damon Albarn made a special mention of the Dubliner, who died aged 32. He said: "The first time we were here was back in 1990. We played at a wedding for Leo Finlay, who has since passed away."
The rockers played an indulgent collection of their songs spanning three decades.
Earlier, Lily Allen told fans she changed controversial words in one of her songs because she had a young Irish cousin in the audience.