Brie and Dave, 30, got engaged in August, after dating since 2012.
The couple has generally kept their relationship private.
“They are so in love,” James said at Hilarity for Charity’s annual variety show in Los Angeles, this year called James Franco’s Bar Mitzvah, benefiting the Alzheimer’s Association. “They just love each other.”
James echoed that feeling in an Instagram soon after Dave proposed (popping the question with a one-of-a-kind rose gold ring by Irene Neuwirth, set with a rose-cut diamond).
“Congrats Davy and Allison!!! engaged!!! I WUUUUUV YOU” James, 37, wrote.
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Brie, 32, opened up about her engagement to PEOPLE last month. “I have an incredible fiancé,” she said. “He’s so wonderful.
“He’s just the sweetest man I know. And he’s so funny and incredible in every way.”
• Reporting by MARIAH HAAS