I have a user that has requested we copy her Shared Documents library from SharePoint 2007 team site to an existing SharePoint 2010 team site.
Can this be accomplished with OOB STSADM export/import commands?
You can not do it with export/import.
Depending on how complex that doc lib is, you might want to copy that files manually or migrate the database that contains the library.
Maybe (maybe, because I have not tried it) you can save the list as a template and modify it in a way that you can use it in SP2010. But I don't know if it is supported. You have to...
Found it here
As noted by AlexPoint, you can't do it with stsadm. There are 3rd party tools to do this, but Bamboo Solutions has a pretty good overview of migrating lists from 2007 to 2010 without them. AlexPoint shows what I think is the simplest method above. Note, though, that if you have a lot of items in the list (thousands), it might not work. The other three options are (hit the link above for details):