Heres a test VFX shot of Rey shooting out Force Lightning instead of the Force Push to signify her instability, the compression makes it look slightly weird but it’s okay: https://streamable.com/cqtffo
That would work if something reached Finn, but it feels odd that it doesn’t given that it looks so strong.
I think for the effect to work seamlessly it would need to be more subtle, like tiny tendrils running along her fingers like in the Palpatine scene accompanied by a little sound effect. If the effect gets large enough that Rey would have noticed it visually, it’s gone to far imo.