To be fair, the target IS the current Mand'alor.
However, IC, Olivia doesn't view Munin as worthy of the title. In her views, Mand'alor and Manda'yaim are synonymous. Thus the "Mandalore of Mandalore" thing. Check the wookieepedia page for more details on that part. And since Olivia is an Alor who used to sit on the Alor Council, but left to tend to her clan, she's got just enough pomp to think she should sit Munin down and give him an earful about leading his people to abandon Manda'yaim. She sees it like a father teaching his children to abandon their mother. In her views, he lost the title of Mand'alor as soon as he took whichever clans would follow him and turned his back on Manda'yaim.
Sooo... If Olivia can subdue him, she'll give him an earful and then decide what to do about the Imperial that issued a bounty on the Mand'alor.
Also, Olivia's gear is custom designed to hunt Death Watch FU, from back when they were an NPC group for the civil war arc. Since she never got to play with her toys, I figured that using them to hunt the Mand'alor would be fun.