So what do people actually call her?

[Albertosaurus Rex]

"Megan" of Megan Lindholm obviously comes from Margaret so that pen name might just be explained simply as what she was called before she got married. Whether her maiden name is still part of her official name I do not know. Also, this might seem surprising now that the Lindholm books are all marketed with "who also writes as RH" all over the covers, but the fact that Megan Lindholm = Robin Hobb was actually a quite well kept secret through the years of publishing the Farseer trilogy!

I believe she mentioned in an interview somewhere that the "Megan" part of "Megan Lindholm" is fiction, but I'm able to locate it just now.

In the Netherlands, the ML books are labeled as "Robin Hobb writing under her real name" and then in a larger font below that "Megan Lindholm". But that might not be factually correct...