You need to stand where you can hear what comes out the other side of their mouths...
As this Catholic chart shows at post 467, Jesus is God...The Holy Spirit is God and the Father is God...
If Mary is the Mother of God, Mary is the Mother of all three...
now you do not understand the nature of the Trinity -- three hypostases but one substance/essence. The bearer of one is not the bearers of the others.
If we take your philosophy that they all share the same hypostasis, then your statement is true, because Mary was the Mother of Jesus undoubtedly
now either you believe that Jesus Christ is God or not. If He is God, then what was Mary the mother of?