My husband agrees that it was the wrong thing to say but that because of her age and culture she meant it as a compliment to my bridesmaid

Likely not just a compliment. Definitely more than a compliment. More like, "I wish my son was marrying you instead" and your husband is trying to fence sit/play peacemaker btwn his mother and his soon-to-be wife.

I agree with the other commenter who said that your fiance should make (or at least ask) his mother to apologize to you. That's inappropriate on so many levels.

Additionally, your fiance's actions and how he's choosing to handle the situation raises a concern. You haven't really given any context about your own relationship with his mom, but it stands to reason that there might be some more tension after the marriage and that she's probably gonna make comments like this to other people and/or you directly. In situations like this, your soon-to-be husband needs to come to your defense and let it be known that they are not to treat you poorly in any way, lest he keep them at a greater distance.

I'd talk to your fiance and let him know how it makes you feel and ask if he will say something to his mother about her comments. Or at least, you two figure out how you're going to handle your in-laws as a married couple.