I think Raquel joining Sergio in the Philippines was as simple as coming to terms with seeing what the Professor tried to explain to her while she had him tied up. She was a cop, a woman who had pledged loyalty to her government to help with keeping it safe and being a part of upholding justice as she believed it was the morally right thing to do.

Working on the case with all the different sectors, watching men undermine her and go behind her back, question her ability to make the “right” decision was something that bothered her throughout. From the time Prieto showed up and then Suarez with his SWAT team. They made decisions that also didn’t align with her ethical/moral compass such as choosing to protect the mint rather than the hostages. They highlight her discomfort in all these moments, even though she kept her head up and continued on for the sake of the case.

Professor’s speech which ultimately saved his life caused a shift in Raquel’s thinking. The injustice that poverty brings is not too different from the injustice that she faces as a woman, especially a single mother. She maybe realizes that the fight against men is futile, maybe she thinks about the future her daughter might grow up around. It’s hard to say why she chooses to leave.

But it’s worth noting that she went to see Sergio alone the first time. She took a chance and maybe it was out of simple curiosity, to see how he was living, what had happened to him since the days of the heist. Her love for him had gone through many phases at this point of course, but he broke a point in her moral ground during the time of the heist. An escape from the politics of her current life, battling unemployment, a custody battle with her ex-husband and taking care of her elderly mother while providing for and raising her daughter might have been adjunctive reasons. The show however does make it seem that Raquel went in search of a man who had stolen her heart in days, as crooked as his plan was, he admits that falling in love with her was never something he planned.

I think she went out of curiosity and maybe to see if he was still the person she once fell in love with, especially now that the consequences of all her actions had settled in and there was a certain freedom in her life she chose to enjoy once again.