Nerd Journeys of Triumph usually end up with the realization that a 'normal', 'useful', 'lovable' person was inside the nerd all along, it held them back and they needed to figuratively kill the nerd to let the 'normal person' out, which is and has always been a terrible lesson to tell to anyone in my opinion. Tilly's growth, on the other hand, I've seen as nothing other than her being more confident in her own skin. When she assessed Stamets' state for Saru, she declared he was improving because his skin looked dewey. A tiny bit, perhaps, but a reminder that she hasn't lost who she is just because she's become more confident. And, as said by others before, there was no shell for her to come out of. She always speaks her mind and wears her heart on her sleeve, and I haven't seen any changes about that.