I always keep the maiden name in my tree.
On a similar note, what name do you record in your tree if the spelling changes over time, or if they reverse their first name and middle name, for example?
I usually record the version they most frequently use in adulthood, e.g. the name they sign on their marriage certificate (if they are literate) or on their children's birth certificates.
Some earlier ancestors have three different spellings on their baptism, marriage and burial records!