The Magnolia Palace by Fiona David

 Henry Frick was a wealthy industrialist who built a mansion and filled it with art, with a goal of leaving it to NYC as an art museum. (ed note: I have been to the Frick Museum and it is glorious.) Anyway, Magnolia Palace is set at the Frick mansion in 2 time periods of the past--around 1919 and the 1960s. 

In the earlier story, Lillian Carter is an artist model whose face and figure appear in statues all over the city. Her mother has just died of the Spanish flu and she is struggling to survive. She totally by chance lucks into a job as personal assistant to Mr. Frick's feisty daughter, Helen, and moves into the mansion.She's trying to keep her "other" life hidden from the family and struggle with working for the temperamental family.

The other plot involves Veronica, a fledgling British model who is sent to the Frick Museum for a photo shoot--then gets locked into the museum with a young intern when a huge blizzard hits the city. She finds clues for an old scavenger hunt that Miss Helen had set up for a suitor, which ties the 2 story lines together. There is also the mystery of the Magnolia Diamond, which went missing during the Lillian storyline and which makes a reappearance during Veronica's adventure.

Magnolia Palace would be an excellent way to while away a snowy weekend.