"Her devotion is very apparent,” says longtime pal Anna Strasberg. "Brooke takes care of Teri. There's a bond there. It's not a public thing for show. It's very deeply personal."
When New Jersey police informed Shields, 43, that a reporter and a photographer had checked her mother out of her assisted living facility on May 14, Shields was forced to go public with a painful decision – that she had moved her mother, now 75, into the nursing home.
Shields has released the following statement to PEOPLE: "My mother Teri Shields has been diagnosed with dementia. For her safety, she has temporarily been in a senior living facility, a very difficult decision for me."
Rocky RelationshipRelations with her mom have not always been smooth for the star, who has two daughters of her own, Rowan, 6, and Grier, 3, with husband Chris Henchy, 45. Shields has described Teri – who was widely criticized for allowing her then-12-year-old daughter to play a child prostitute and appear nude in the 1978 film Pretty Baby – as an alcoholic. In 1995, Brooke fired her mother as her manager. (Teri divorced Brooke's father, Frank Shields, when Brooke was an infant.)
But the bond between mother and daughter, at times strained, was never broken. "It was us against everybody," Brooke recently told More magazine.
Shields's friend Anna Strasberg, who has hosted Brooke and her mother for Thanksgiving and other holidays, notes how Brooke dotes on Teri. "When Brooke has her mother at gatherings, she knows that her friends know the situation and Teri's not pushed aside – she is part of her life and that is so beautiful to watch," she says. "It is painful and it's beautiful."
"They watch the floats and the [Thanksgiving] parade go by,” adds Strasberg. "Brooke is very tender and keeps watch over her to make sure she is okay, and that someone is talking to her. Teri may not be able to always have lucid moments, and she may not always be able to voice her feelings, but some moments are beautiful."
Another of Brooke's friends, Broadway director Kathleen Marshall, says of Teri's deteriorating health, "[Brooke]'s very direct and honest but doesn't dwell on it."
For more on Brooke, including more details of her evolving relationship with her mother, pick up the new issue of PEOPLE, on newsstands Friday