Not sure why you're trying to waste time on over-analyzing some random shadows or the limb kinematics - video was obviously re-encoded few times (as usual for YouTube thieves who put someone else's video on their own channel ) so there are plenty of artifacts and loss of all details from that.
As for "why" this happened - woman could be drunk, on drugs, or have a severe case of hypoglycemia (low blood sugar) which will basically make you act as a "zombie" without any drugs/alcohol involved.
As for "why" this happened - woman could be drunk, on drugs, or have a severe case of hypoglycemia (low blood sugar) which will basically make you act as a "zombie" without any drugs/alcohol involved.