There is one unspoken rule in LotR LCG - heroes don't lose/gain stats when they swap spheres.
I don't understand your unhealthy urge to lower her willpower. Eowyn's willpower is her mark in this game.
As for starting willpower, Spirit Eowyn has 4(+1 per player potential) wp, Elrond, Sam and Thorin got 3 wp and guess what? It's their base wp, without any boosts. And guess what else? Their abilities are not wasted on just giving willpower to the party.
The very purpose of Theoden is to make tactics into questiong, and I see no problem in doing so as most quests strike you with heavy threat and this early willpower surge is a compensation for total lack of willpower in allies later in the game - it simply won't grow past that.