The TV beauty was introduced to Dykstra by her friend Joanna Garcia and her husband, New York Yankees player Nick Swisher, and has been enjoying dates with the Washington Nationals infielder for a few months.
The rumoured couple also enjoyed a vacation together in Florida earlier this month (Mar12), with Dykstra 'tweeting' Sigler after the break, "Had an amazing time with you, i miss you so much. The last week flew by."
A source tells the New York Post's gossip column Page Six, "Things are going really well. I haven't seen her this happy in a long time."
Sigler has previously dated her Entourage co-star Jerry Ferrara and American footballer Mark Sanchez, who she split from in 2010.