In principle you can model the interaction between the electrons and the particles in the barrier and the whole system evolves according to Schroedinger’s equat

In principle you can model the interaction between the electrons and the particles in the barrier and the whole system evolves according to Schroedinger’s equation and will be described by a wavefunction. This wavefunction may be a superposition of states where the electron goes through the slits and states where it doesn’t. Until there is a “measurement” - a “detection” which is “amplified” - you cannot say what has happened to the electron: every outcome remains possible and the system remains described by a wavefunction. If the detection happens first at the screen there will be a probability of finding the electron at each position and a probability of not finding it at all. Note that the detection on the screen is done using a scintillator/photomultiplier or something like that to amplifify the detection of a single electron into a measurable electric signal.