She's determined to see this through.

X17online can exclusively report that Jennifer Garner dropped by to visit Ben Affleck this morning at his Malibu rehab, just two days after staging the intervention that got him into treatment.

A source tells X17:
    "She wants to support Ben -- he's the father of their kids and no matter how upsetting his actions are, she's always going to stick by him."

From what we've been hearing, the first few days of "detox" has been rough, and the Peppermint star wants him to know he's not alone in his recovery.

The same source added:
    "Ben is on the fence about staying; Jen wants to continue to remind him why he needs help. It's all about the kids -- he'll never get to see them unless he stays straight."

He's lucky to have her in his life!