Once you have completed the tutorial (if you have read my previous cheats, then you can have the opportunity to increase your combat, destruction and restoration skills).

Now when you leave the sewers, you need to go to Vindasil, where Umbra is hiding.

Now this is the suicide part of it, you need to cast a fireball spell and run as fast as you can to the imperial water front, where you can join the thieves guild and the guards will make an attempt to attack her and will fail badly and not even the important characters that can't can even stop her.

TNw as soon as she kills a-lot of imperial guards and then you can take the armor and if Umbra dies then feel free to take her armor as well and her sword.