Should I get my baby baptized or wait until she is old enough to make the decision herself?

You should wait. The Bible links baptism with belief and repentance. For example:

Repent and be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins (Acts 2:38)

But when they believed Philip as he preached good news about the kingdom of God and the name of Jesus Christ, they were baptized, both men and women. (Acts 8:12)

Baptism, which corresponds to this, now saves you, not as a removal of dirt from the body but as an appeal to God for a good conscience, through the resurrection of Jesus Christ, (1 Peter 3:21)

Note the things that accompany baptism: belief, repentance, confession and conscience. But a baby knows nothing about what is going on, and she can’t believe, repent, confess or have a conscience about what she is doing.

So leave it to your daughter to decide when she is old enough. In the meantime, teach her about God, his plan of salvation through Jesus, and the kingdom of God.