RL, my dd started full time school in January too, she's 4.6, and I've seen a change in her behaviour although not to the extent of your dd but that may well be because she's an only child so I can focus on her in a way that it's hard to when there are two who both need attention.
What I've found is that like someone else has said, she's working so hard to be 'good' at school that when she gets home it's almost like she needs to let off steam. She demands attention in a pretty much constant way, every five seconds it's 'mum! look at this' or wails of 'I can't do it' before floods of tears. This isn't like her at all. Literally she won't leave my side or be out of my attention for a minute. If the phone rings she creates such a fuss it's almost funny if it wasn't so infuriating. One of the other mums at school said her little boy is very angry with her about leaving him all day, he actually said that to her, and although dd hasn't said that to me I'm wondering if there isn't some of that going on.
I think some of this transition to being a 'proper' school child is very trying for them and as much as possible if we can keep our patience and try to see it from their point of view we can just about stay on top of it.
I think you were right about sticking with the 2 stories though, you have to stick to your guns. And I really feel for you about the guilt over her screaming herself to sleep. Dd sometimes sobs herself to sleep and it breaks my heart.
Oh yes, the other thing of course is tiredness. Is your dd much more tired now she's at school? I've found that doing the whole bedtime thing much earlier is a big help. That way when things start to go a bit wrong there's enough time to sort them out without bedtime getting ridiculously late. I now aim to have dd totally ready for bed by 6.45pm at the latest then we've got 45 mins for stories and shennanegans and she still manages (mostly) to be off by 7.30pm.
HTH?