In general, if a Mo’min proposes one should not reject the proposal unless there is a valid and legitimate reason. Between you and Allah, if you believe the reason is justified, then that’s ok it should not take away tawfiq in finding a pious spouse in the future. The tawfiq is taken away if you’d say no due to materialistic reasons, such as preferring a non-Mo’min over a Mo’min because the non-Mo’min is richer or has a greater social status.
But if you believe the reason is legitimate and you are determined to marry a Mo’min in the future and you’d never prefer a non-Mo’min over a Mo’min then it should not affect your tawfiq Insha’Allah.