1- Be BFF with Morgana and be sure that Morgana hangs out with you more
2- By doing the way above, get to the second step and make Morgana say to Morgause "Now that I got the crown, you can get your ass out of Camelot my dear sister."
3- Be very nice to Cendred and let Morgause see you&cendred together, talking laughing etc...
4- And when you are very well with Cendred, make him kick her out of his castle so that she'll be alone in every ways
5- Take the video of Morgause&Arthur talking about what Uther did to Ygraine, yet Arthur kept talking to Uther. Then make her watch this video 10 times, see how she goes nuts.
6- Tell her "You suck at magic, you cannot even protect a simple goblet from a servant!"
7- Ask this to her: "Maybe you are stupid because a big stone fell on your head when Merlin blew the whole place up?"
8- Show Morgana's stupid smirks to her with photos and videos over and over
9- Ask her where on earth she finds those stupid magic words that she cant even spell well?
10- And finally tell her that her choice of soldiers were so bad that even though they were invincible, they couldnt protect anything.
11- Tell her if she keeps killing men who luv her, or like her, she'll die alone :(

I made all this up and I know they suck xD But as a hater of Morgause, Im happy to find some ways to annoy her xD if u find anything else, tell me and I'll add it:)