Last week, Gabby had a perfect situation. Amber M. was in an elimination that was blatantly physical. She had the advantage going in, but she passed on the opportunity. Now Amber B. has a skull and Gabby still needs to get one.
On the surface, this seems like a huge mistake. Now, is Gabby screwed longterm?

Of course, we also need to consider that Gabby is in a partnership. Devin’s game was at risk, and she could have gone into elimination only to have Devin face Cory. It’s understandable that she doesn’t want to jeopardize his game, but would it really be that bad? Devin could have lost to Cory, Gabby could have gotten a new partner, and Gabby would now have a better shot of getting power again. Of course, this didn’t happen, but it doesn’t seem like this partnership should have influenced her decision so heavily.
Allegedly, Gabby wanted to send in Amber B. because she thought she might lose to Amber M. As we know from episode 9, Gabby and Amber M. remain close friends while they feel betrayed by Amber B. In Gabby’s eyes, facing Amber M. would guarantee the alliance is broken.
Even though Amber B. won this elimination, she will likely be an easy target once the girls need to steal skulls. Perhaps Gabby felt more comfortable facing Amber B. if the opportunity arose. If Gabby manages to snag the fifth skull, she won’t be the easiest target. Amber B. will be just as susceptible.
Gabby’s decision was likely motivated by friendship more than just getting her skull. The episode doesn’t emphasize this, instead we see Devin try to force a power trip. Gabby is made to look like a fool rather than a loyal ally.
From a purely strategic game, Gabby did make a mistake. From an alliance-based game, there is some logic in her decision. If Gabby loses in elimination or fails to get a skull, her decision to skip this elimination will be a huge blunder. This season moves too slowly to pass an opportunity, and Gabby might have given up her biggest one.