This is what I believe is a word from the Lord:
God Will never lead you to a person who differs with regards to your faith in Christ. Never compromise Lord Jesus Christ for anyone, no matter how attracted you may be (physically or otherwise) toward him/her.
The best way to explain the attraction between the two is this: It’s the ‘closest’ match thus far in every aspect but it is “not” His Will because the “belief in Christ” didn’t match ‘perfectly’ to the point of “doctrine” (the most important factor to determine whether a person is to be your spouse or not with regards to God’s Will).
Thus, such a couple may break-up, learn positively, and move on to find a person (if they will) to marry by finding a “perfect match” in “belief” first whilst heading their separate ways.
Difficult it may be, it is best to “leave” that person than to drag the “doctrinal differences” into “marriage” for no matter what “human words in error/lust or otherwise” might be exchanged between the two people in concern (during courtship prior), “God Will forgive” their “error” in getting together in the first place due to “wrong oversight in belief” plus “it’s not the unpardonable sin.”
Thus, I believe that the Wisdom of the Lord teaches to “end” any such relationship because it’s “harmful” both ways though both are Christians with “doctrinal differences”.
We may maturely take “our error” as lesson instead to ensure that any “marriage -aimed” relationship must be between two people (male & female) who are “not doctrinally different” (equally yoked in belief).
Any other differences, with regards to the things of this world (e.g. your spouse doesn’t like the music you listen to) may be “beared” (as your freewill choice) because it does “not” affect the most important spiritual walk with the Lord (faith).
Thus, forgive each other for the errors (especially those done in words/acts toward each other) and thereby be healed of any heartaches (emotional feelings too) and be “free” in Christ’s Holy & Gracious Name to seek God’s Will in “faith” (belief) which matches first even in an Eros-type-love for possible marriage (deep wisdom).
Shalom & may the Peace of God which surpasses all understanding guard your hearts and minds in Christ Jesus, Lord & Blessed Saviour, (especially those going through such a lesson).
Remember, that in that error too, you tried & learned that it’s not a match in “doctrine” and hence, no regrets in “what if questions” (which only plague those who didn’t try).
*The sooner a relationship which is “not” His Will is stopped, the lesser the sin and quicker the forgiveness of the Lord toward both Christians involved bringing His Grace upon them as even “they both repent” of this error (“relationship” differing in “doctrine” not knowing each other’s stance on it “previously”).
Point: Always start such a relationship with a “match” in “belief” (doctrines in Christ) first rather than physical or other emotional attractions (the common mistake).
This is how I believe that God brings a true believer back into their “right senses” minimizing the error and sin due to this too.