5:45 AM PT -- Alison Brie responded on her Instagram Story posting a pic of the two from SAG Awards, saying, "Nothing but love for @chrissymetz !! Rumors can't keep us down!"

Chrissy Metz seems to have forgotten how a microphone works -- 'cause it sounds like she called fellow actress Alison Brie a bitch ahead of the Golden Globes ... but Chrissy says that isn't the case.

The 'This Is Us' star was being interviewed on the Globes' own Facebook Live pre-show by AJ Gibson and Missi Pyle when toward the end of their chat, AJ asked Chrissy if she knew who Alison was. Chrissy sarcastically responded, "Do I?"

AJ said Alison was on the other end of the red carpet, and as the camera panned to Alison with another Globes host ... Chrissy can be heard saying what sounds a lot like, "She's such a bitch." The audio fades out a bit as the line is delivered.

It's unclear if Chrissy was aware her mic had picked up the comment, but it doesn't appear Alison heard her as she didn't react. Chrissy commented on the news ... calling the "bitch" angle fabricated, and saying she adores Alison and would never say a bad word about her or anyone ... adding, "I sure hope she knows my heart."

It's odd though ... Chrissy doesn't clarify what exactly was said.

Alison has been nominated for her first-ever Golden Globe for her role in "GLOW" -- and Chrissy, of course, has been nominated a couple times already for her role on the NBC drama.

Weirdly enough ... they've posed together at events before, and there doesn't seem to be any surface-level bad blood between the two stars.