I hope that was intended as a joke. It follows the same logic as this:
- Mary is the mother of Christ.
- The church is the bride of Christ.
- The church is the body of Christ.
- Therefore Christ married himself.
- Therefore Mary is our mother-in-law (yuck).
- God is love.
- Love is blind.
- Therefore God is blind.
- We might conclude that Christ's accidental marriage to himself had something to do with his blindness.
Mary was the literal mother of Christ. Christ is the figurative head of the church (which is his figurative body, naturally). This statement doesn't make her the figurative or literal mother of anyone but Christ (lest we be guilty of abusing an analogy). Otherwise, we should be venerating Heli, the Grandfather of all Christianity, which no one has suggested.
Friends don't let friends abuse logic.