There was nothing to autoattack for her to lifesteal. Plus, Teemo has a Morellonomicon, which f**ks her healing anyway.
Jinx should certainly die to a shroom at this point
No. No champion "should" die to a single f**king ability. What the hell kind of game is that?
You choose what to build when that can make a difference.
Do you, as an ADC? The way I see it, Jinx already has a defensive item, PD, but her needing PD to be up to not die to a single ability is a joke. She already has a QSS, but Mercurial Scimitar only gives +5 magic resistance when the item's completed anyway, and the QSS/Merc active would do nothing for her here. If she went for the MR item earlier, she'd do no damage because ADC damage without going directly for full damage items is godawful. The mistake in the build I see is that Jinx went for 100 percent crit. Maw of Malmortius is off the table because she already has PD. So Jinx should have...gone Merc Treads, which would sacrifice the most gold-efficient source of attack speed on a champion that only auto attacks (and probably still not have saved her)? f**king Wit's End? A completely normal, full ADC build would die in this scenario. The only difference between Jinx's build and a normal ADC defensive build is that Jinx has -5 MR.