The casting felt off in places; Bella Thorne doesn't seem like a fit as a character who is supposed to be an expert in quantum physics. This isn’t about her gender or appearance—plenty of women can portray scientific professionals believably, like Jodie Foster and Laura Dern—but the role just doesn’t work for her. The movie would have been better if Vivien seemed knowledgeable about what she was doing. The quantum physics aspects don't really do anything except act as a strained comparison to falling in love. Vivien herself appears unsure of her area of study, calling it both "simple" and "complicated," along with “fascinating” and “exhausting.” All we see to support this are equations scribbled on her bedroom mirror, implying she’s meant to be like Will Hunting. She describes herself as a "numbers girl"—presumably referring to the kind of numbers associated with a certain phone number—and when questioned about the connection between math and love, she says something along the lines of there being numerous figures linked to the concept of “love,” which once made sense to her but now doesn’t. I'm not convinced either. What numbers are these, and how do they relate to love? However, Vivien apparently fails a significant test at least once (it’s frequently referenced but never clarified), something she has supposedly been preparing for over a year, so perhaps she is experiencing the Dunning–Kruger effect.

Source on TMDB