Thanks for the question.
It is not possible to fully know the mind of God in any circumstance, but the answer could only be maybe.
Marriage is a Sacrament that two people confer on each other, which involves vows and a consummation when two become one flesh. So in theory, the answer could be yes, because technically, at least in the Roman Catholic Church, a priest is not required for the Sacrament, however, marriage is also a public institution as it represents a sign to others, so it has a place in the Church with official witnesses, and a priest is the ordinary witness on behalf of the Church to insure the marriage is licit. So many factors could impede the authenticity of the vows; in a quest for an annulment, such a marriage would likely not stand. We imperfectly try to understand the will of God, but only He knows His own Mind and all the facts that inform His Judgement.
All that being said, generally the immediate circumstances affect the validity, what we call God's blessing of a Sacramental marriage. In a situation where two lovers were not in a place to have witnesses present, (some war torn apocalyptic environment might suffice for your imagination, having said the vows, and consummated the marriage, etc.), God may very well have blessed it.
In that hypothetical, they would still need to later have it blessed in a church to insure that, in her eyes, it was licit and valid (presuming there would be one).
Essentially, a deliberate attempt to circumvent the Church would not likely have God's approbation.
Hope this helps,