I completely agree with you, a modder probably could even find someone who could cast her voice good enough just for the few lines needed, well good enough to pass anyway. But you would still need someone willing to wade through the related quests, scripts, etc.. Easy enough (or maybe not) for someone who knows what their doing for normal followers but they did go to alot of effort in making her character different.
When I've made followers before though they could only be married if you chose one of certain voices for the NPC. If you happened to choose a wrong voice they could not be married.
May have been when I was reading about it that they got it wrong.
This is probably all acedemic anyway, the whole marriage system in Skyrim svcks big time, unless you have some mods it's not like your going to see or get any action even if you do marry. The only character my female warrior married was Ysolda, they slept together once when she first moved into Hjerim and then Ysolda never slept again.