Sara Foster Jokingly Trolls 'Mom' Katharine McPhee to 'Dress Age Appropriately'

Sara Foster is calling out Katharine McPhee once again!

The 37-year-old daughter of David Foster took to Instagram to share a photo of herself posing in a bikini alongside the 34-year-old singer – and had to tease her future stepmom just a little.

“When your mom refuses to dress age appropriately,” Sara captioned the below photo.

Katharine then commented on the photo writing, “I can’t even think of a good response.”

Sara commented back saying, “as long as you keep looking this good in a bikini I will be writing captions like these.”

Katharine and her 69-year-old fiance have been vacationing in the Hawaii with his family for the holidays!