Let me put it this way. In the book, you have a morally grey Tyrion (tries to do good, but isn't quite Ned Stark and will certainly cheat, lie and murder to climnb up the ladder) and a morally grey Shae (not a monster, but a selfish and manipulative gold digger who doesn't care about anything except her luxuries and who has no qualms about humiliating Tyrion at his trial). When everything crumbles down, their actions make sense; Shae wants to keep her gold and jewels, and is probably terrified of Cersei and Tywin, so she betrays Tyrion to Cersei and fucks Tywin (the hypocrite) to keep her status and possibly her life. When confronted by Tyrion, she tries to manipulate him by playing up the scared part, but she just goes a wee bit too far and Tyrion sees through her. That she's in Tywin's bed at the time doesn't help. Tyrion, by now a defeated, broken and humiliated man, kills her in a rage.
Now let's look at the TV show. Tyrion is hardly grey anymore. Shae is a very different character indeed, but in more sense than one now. Initially she was still just a gold digging whore like in the book, but she had different origins (foreign and highborn), and she was sassy and kinda bitchy. Those were the differences with book-Shae, who had lowborn origins and who acted all sweet and charming (as part of her job). Now, though, they've made her all tough (the knife "no one is raping me!" in Blackwater), fiercely protective of Sansa, contemptuous of rapists (book-Shae rolled her eyes at the suffering of a woman who was gang-raped, "all they did was fuck her"). It's unclear if she genuinely likes Tyrion or is just pretending as part of her job, but all indications show it's the former, especially with considering all the rest. So, she's more likeable.
Yet somehow, we're to expect good-guy Tyrion will end up murdering a woman who is protective of Sansa (who will become his wife)? Unless they throw in some weird twist, I just don't see that happening. You suggested the jealousy angle, but that was just bad writing. It's not remotely believable that Shae, even TV-Shae, would react wildly to Tyrion calling a pretty lady pretty and be offended that he's "such a perv" (FFS, she's an experienced whore!). It was completely anachronistic and out of character (even for TV-Shae). But even if we go with this, and Shae is jealous of Tyrion's wedding and physical attraction to Sansa, why would she betray him at the trial when it'd also incriminate Sansa, whom she's protective of?
I just think this new story is a mess, badly written, badly acted, and most of all, unnecessary, as there were no time or budget restrictions there and they could simply have kept Shae and her story as she was from the book. They tried to improve upon the book, and once again, they failed miserably.
