Well, as I move on to paint the Elsa Zombivor I thought it might be an idea to look at her statistics.
Break-in is retained at Blue level. This is a silent door opening ability. Silent is now important!
Yellow level gives a free Ranged Action.
At Orange level (this is where it gets interesting) Slippery is still available but Rotten is introduced as an option. Rotten allows Elsa to be totally ignored by all Zombies. This has exciting possibilities. For it to come into play, Elsa must not make a noise in her turn and not take a combat action. She can move freely. It fits in really well with the whole 'cat burglar' theme. Late in the game with lots of Zombies around this could be a fantastic rule to allow the claiming of objectives. I just knew I would like this girl.
Finally there are options for Red level a) +1 free move which could be very handy especially combined with Rotten b) +1 free Combat Action or c) Super Strength which converts all Melee weapons to damage level 3 making her an aggressive combat monster.
I like the Rotten and +1 free Move Action combination.
It could be handy to have Elsa combining Rotten with Break-in to open difficult to get at doors maybe before someone in the group hits Red level.
Elsa is definitely an cool option and could be very helpful for the group. Turning her into a Zombivor early might also be worth consideration, but only after she has hit Orange level for the Rotten skill.
And lets face it - she looks fantastic ;-)