Agree, marriage shouldn’t be determined with small things.
But what bother you about the smartphone?
What is the problem with it?
When you understand you’re problem with it, you can find a solution or a compromise on it…
Is it unfiltered internet? Games? Addictedness?
All can be solved, and talked about it with the girl, your issues with it and opinions…
I believe anything can be solved through communication.
Speak to her, and tell her your concerns