I have a 6 month old EE hen who has started showing some signs of being broody over they last week or so. Do to some outside circumstances I haven't been able to collect/wash eggs for a few days, which allowed them to build up a bit. She is currently sitting on twelve (!!!) eggs, presumably fertile as she is in with a rooster and one other hen. The problem is, I'm not entirely sure how long she's been setting; I've been shooing her away from the nestboxes for some time now, and I know I chased her away last night, but I don't know how consistent she has been, exactly when she started, or how far along her eggs may be. I candled them, and I don't see major differences; the eggs are colored and thick-shelled, so it's a bit difficult to discern, but they're definitely not more than a couple days along as there aren't obvious differences from their sister un-incubated eggs from another nest. I don't want chicks right now, but I also don't want to toss eggs with chicks developing inside. I've told my mom (I'm a college student living at home) that I'll get rid of them, but I keep worrying about it and it's making me really anxious.
So my question is: how far along is too far along to take them and get rid of them? Has anyone else experienced this? Maybe I'm overthinking it; I just don't want to pointlessly kill anything. I mean, I don't even kill bugs if I can avoid it, it makes me queasy.