To come across a mate-beggar is when you have someone who follows you about constantly asking for you to be their mate/lover in the game. It's highly annoying, and they tend to bug you until you log off or they do. Though my suggestion is to just play along until they log out and then block them. Or just block them right off the bat.
They are a mythical species that prance around all the realms, (mostly Bonfire Island) hiding amongst the shadows waiting for their next prey to pursue. They are determined to make you their 'mate' and will go to the ends of the world to make you love them.
...Some barely live to tell their experience...
(http://ak-hdl.buzzfed.com/static/2014-04/enhanced/webdr04/20/9/anigif_enhanced-buzz-14085-1397998807-4.gif)
Heheh psych