The couple are currently spending time together on the sets of 'X-men' sequel, reported Aceshowbiz.
"They started the shoot in April as just friends and then one day they started kissing. One thing lead to another and they hooked up. All her old feelings came rushing back. Jennifer has been telling people she's in love again," a source said.
The couple showed signs of being friends post split as they were seen together in public earlier this year.