A source told ET that the actress is "relieved" that the father of her three children -- Violet, 12, Seraphina, 9, and Samuel, 6 -- is "in a safe place."
"This has been a rough few days and [Jennifer] wants nothing more than to feel [Ben] is getting the help that he needs," the source said, adding that Garner has "been Ben's rock" throughout this process.
"She is used to putting on a brave face, and handling Ben's addiction, but the process has been very exhausting for her,” the source continued. “She won't give up on Ben because he is the father of her kids."
"Ben trusts Jen entirely and followed Jen's instructions," the source added. "This time he sounded willing and ready on all counts. Friends who saw Ben's rapid decline are breathing a huge sigh of relief. They have high hopes for a recovery."