Well, start with the outside walls... sure she knows where she wants the front and backdoor by now... and if you gotta change some windows here and there whilst builing... you gotta be a bit flexible you know, lol.
I can understand she keeps changing her mind. Difficult to decide on certain things. I know ppl who built a house from scratch, the idiots put the living room on the right, the huge garden on the left, with a garage in between, attached to the house. What's the friggin point of that? No one can see or enter the garden from the living room, they have to walk all the way round the back to get there. So they ended up never using the garden. Totally stupid! If their kids played in the garden, they couldn't even keep an eye on them. Had they swapped location of the garage and living-room, it would've been the perfect house (they bought two lots for it, 1 is the garden that now isn't used).
So yeah, you might wanna think it through. And changing your mind, oh well... she's a woman, right, it's her prerogative, hahaha
Good luck with it, lol