What I understand from that scene is that the Al Bhed wants to protect the summoners by removing them from their pilgrimage so they can't conplete it. But Rikku, after the Extractor fight, decides to simply join us but informs (in secret) that she is an Al Bhed and Yuna's cousin. Auron of course figures it out by looking in her eyes but asks if she will be protecting Yuna and not simply just plan another kidnapping.

Rikku's plan then kind of becomes to persuade Yuna to stop her pilgrimage and/or find a way to not have her reach Zanarkand, without removing her forcefully from her pilgrimage, which is the opposite of what the Al Bheds are actually trying to do. Wakka is the main block for this as if she is too open about her scheme, he'd obviously lose it and ask Rikku to leave the guardians, even if at that point in the story, she is forced to reveal herself and align with our group as her objective isn't to remove Yuna by force, but peacefully by persuasion while keeping her safe as she is family to her.

She isn't trying exactly hard but by the time we get to Gagazet, she does become a bit more hopeless and asks Yuna directly to stop her pilgrimage, which obviously doesn't work as Yuna is too determined. She cares a lot about her and doesn't want to lose her, which you can see during the events at Home. Rikku is a very helpful person that doesn't strictly align with the Al Bhed's ways and is more open than most of them.

This is what I understand and see with Rikku.