Mary McDonnell is not afraid to admit that Hallmark is her kryptonite.

The Dances with Wolves star, 73, tells PEOPLE that she wasn’t always tuning into the Hallmark Channel around the holidays — “sometimes I would and sometimes not,” she says — but lately, that’s changed.

“In the last couple of years, I’ve just gotten completely addicted,” McDonnell admits from the Ireland set of Twelve Dates ‘Til Christmas, the holiday series she stars in alongside Mae Whitman, Nathaniel Parker and Jane Seymour.

She recalls a phone call with her agent, Jonathan Power, who called in the middle of the afternoon one day in December.

“He said, ‘Are you busy? What are you doing?’ and I said, ‘Well, I am a little busy.’ He goes, ‘Well, what are you doing?’ and I said, ‘Well, I’m watching a Hallmark Christmas movie.’ He goes, ‘At 4:00 in the afternoon on a Wednesday?’ and I said, ‘Yeah, that’s all I’m doing right now.’ ”

The conversation then shifted focus, “because he loves them too,” she says, and when he asked whether she’d ever be interested in starring in one, her answer was: “Of course.”

“Now that I know what they are and how amazing [they are], and how it is supplying, in my opinion — it supplies everyone — but it really helps women, because romance is a very delicate thing and we are losing it, I feel, as a way to communicate in the world,” McDonnell says.

“And so when you go into these worlds and see [romance] enacted in such a beautiful and innocent way again and again and again, you honestly start to feel like it’s possible. And I think that’s wonderful.”

In Twelve Dates ‘Til Christmas, McDonnell plays Delilah, mom to Kate (Whitman) and divorced from her father, Mac (Parker). Delilah is a “globe-trotting American always on an adventure,” per the official synopsis, but she makes a surprise appearance in Kate’s hometown of Blexford, England, around the holidays, throwing off both Kate and Mac’s plans.

She says she was drawn to the role both because of her love of Hallmark and because of Whitman, 37, with whom she starred in Independence Day with in 1996, when Whitman was only 7 years old.

“We haven’t seen each other for so long, and she was so young, but it really honestly felt like we had seen each other a lot. There is something there that’s so just there,” she says of reconnecting with the Parenthood star. “She is just a gem, an absolute gem, so I’m thrilled.”