Amanda Seyfried and Bret Michaels donate to children's charity

Amanda Seyfried has donated $25,000 to a children's charity after agreeing to match a pledge made by rocker Bret Michaels.

The Mamma Mia! star was attending the Eric Trump Foundation's 5th Annual Gold Invitational + Gala at Westchester, New York's Trump National Golf Club, where the Poison frontman was performing.

The fundraiser was aimed at raising cash for St. Jude's Children's Research Hospital and Michaels decided to kickstart the big donations to the cause by promising to send a cheque to the organisation at the end of his set.

He decided to up the ante at the event by calling on partygoers to follow his lead and match the amount - and Seyfried was one of the first to respond.

The actress was at the gala with her new boyfriend, New York real estate executive Andrew Joblon, a boardmember for the Foundation.

A source tells People.com they've been dating "for about a month", adding, "They are calling themselves a new couple."

Seyfried split from Cruel Intentions actor Ryan Phillippe in May (11), before reportedly reuniting with Cooper, who she dated for three years after meeting on the set of their 2008 movie musical Mamma Mia!.