I have a VA who does a lot of things for me, and I am wondering if she can also do some posting in the forum while still assigning that post to me OTHER than having her log into my account? Is that possible?

For topics and posts, you can do that by using a 3rd-party resource: 

 

 

https://www.sosinvision.com.br/index.php?/file/36-linked-accounts-post-as/

Not in the core, other than them logging in as you