I had quite a few back and fourths with nessa about his bittercup mod.
The one you can find on loverslab works perfectly now, and you definitely need the mojave delight resources.
The only way I can think of as to why you might get away with not having them is if you have a mod loaded late in your order that also adjusts bittercups appearance, which will at the same time break Nessa's mod.
I spoke with nessa sometimes about bittercup and Sydney Updates(finally sent mine to her), she's occupied yet with her, also i sent the the converted Alt look for bittercup(the popular goth one from Fo3 nexus) that i converted a long time ago, it will take some time, since she's planning to update her with updated lines for New vegas(like the DLC's) and a better AI
if i was you, i would wait until the final update, only a few Fo3 companions works with JIP and TTW, and some of them has some tricky scripts and behavior
