This is something that I also have had trouble with. It appears you are using the Douay-Rheims translation, but a lot of versions have it translated with this grammatical construction. However, I discovered that the NRSV translates Luke 2:34-35 as:
Then Simeon blessed them and said to his mother Mary, “This child is destined for the falling and the rising of many in Israel, and to be a sign that will be opposed so that the inner thoughts of many will be revealed—and a sword will pierce your own soul too.”
Now I don’t know Biblical Greek myself, but I like to use a literal translation of Scripture when I face issues like this. The one I use puts the words in the same order basically as the one you’re using, but the part about the sword piercing her soul is in parentheses. So it would appear that St. Luke has Simeon saying something to the effect of “The opposition to Jesus will reveal the thoughts of many hearts. By the way, your soul will also be pierced with a sword.” I think St. Ambrose explained what it means that the opposition will reveal the hearts of many. He said that the idea is that the Pharisees and those who should have been expecting the Messiah, but instead condemned Him to death, were angry with God that the Messiah was not a Glorious King who would share His physical riches with them. So killing him shows where their minds really were. I don’t know if any of this is right but I hope it helps somewhat. God bless!
