I approach it sequentially Mercury, given the starting location, solve the method of getting from there to half a metre away.
I agree it appears to be easy to make a w+w theory without the window and shutter being opened. Two recognised experts did exactly that, one if I recall correctly was MWT and the other another brit ex-police expert. But there are two problems with both of their theories - first they don't provide any good reason for w+w, and second they completely forget that in this actual case, the window and shutter actually were opened by someone.
Kids can get out of bed for various reasons, each as valid as the other. Ref your last sentence, even if it's factually true that the window and shutter were opened, there is no evidence as to who by really.It shouldn't really have to boil down to whether you believe the parents or not.
Common reasons for wandering can include sleepwalking, and/or having a night terror, or going to find an adult or visiting a favourite place though in that last example in the pitch dark I doubt most toddlers would do that, though there was a recent story about a very young girl in the USA putting her shoes and coat on in the middle of the night and going to buy sweets IIRC at a petrol station.
This all tends to falls down as normally wandering kids are found, unless the child met some fate such as falling down a hole, or was whisked away and hidden after a hit and run e.g. or the MWT idea that there just happened to be an opportunistic paedophile around at the time who grabbed her ...or a hypnotist who chanted, come with me!!
