There is more than one conflict in a story. Lack of closure is an internal conflict.
In literature, the resolution of the conflict is the denouement. Closure is usually referred to as emotional acceptance, which would mean that lack of closure is a character vs. self internal conflict. Closure might be something a character does or does not feel. If the conflict is unresolved, that might lead the character to feel a lack of closure. It would depend on the character. In that case the internal conflict would remain unresolved.
The resolution will not necessarily be a happy ending. For example, if a character is struggling with his sister’s disappearance, not knowing whether she is dead or alive would bring him a lack of closure. That character vs. character conflict, her disappearance, would remain unresolved. The character vs. self conflict would also remain unresolved, unless the character comes to terms with the fact that she never returns. However if her body appears, both conflicts have been resolved even though they did not end happily. The character may have closure, unless he does not know who the killer is!
In your example, the marriage is a resolution to one conflict (external) and the admittance of feelings is a resolution of a different one (internal).