If I am not mistaken Angel re-joins the Fanged Four during the Boxer Rebellion for the first time in two years after Darla kicks him out in Romania. He spends maybe a week or so with them , during which time he tries to impress Darla by going back to feeding on people - but as she soon discovers he cannot bring himself to kill an innocent, but only kills murderers and rapists ( which are plenty of around during the rebellion as the streets are teeming with people pillaging and killing other people). After Darla discovers him trying to save the missionaries from her ( just to remind you of the actual content of the episode vs the re-imagined 'feud' supposedly going between Angel and Spike there) Angel runs away from her and the group again - carrying the baby. Supposedly he never rejoins the group or meets Spike until the submarine episode in mid 40 ties. Spike kills his second Slayer on his own , again, in NY 40 or 50 years later, but it is implied that he stalks and tries to tackle a few more - but they all either die before he gets to them or prove to be too strong. Now, for the life of me I cannot see any opportunity for Angel to 'get jealous' over Spike's 'achievements' during the brief stunt in China - he was too preoccupied with his inner conflict of not being able to see people as cattle anymore vs his need to belong with somebody - anybody - even Darla. So, yeah, the situation was not as simple as Spike-y getting drunk on the aphrodisiac of the 16 years girl's blood - calling for her mother - and Angel feeling 'jealous' while trying to save a baby from Darla. Consequently, Angelus upon his reappearance just stepped back into his own shoes and started slapping Spike back into submissive role because it was in his basic nature - not that he needed an extra drive for it. He could not have known about the second Slayer, and besides, I think he thought that attacking Slayers was blazing stupid, not any kind of vampiric badge of honor. When he was faced with Faith later on he preferred to deal with her in his signature subtler, backstabbing way - same way he took down the Beast. ( Mind that I don't find either Spike or Angelus in any way appealing as personalities - but I kind of prefer smarter villains.)