It sounds like London had a seizure. Since she has recovered, it isn't a veterinary emergency. You can call on Monday. They will probably tell you just to watch her and see if she has anymore before they recommend bloodwork. Has London ever had a bile acids test? All Yorkies should have one, but especially if they have had a seizure.
Blood sugar drops very low during a seizure which is why her gums were white. Giving a tiny bit, about a teaspoon, of vanilla ice cream or nutrical as you did can help her recover more quickly.
What you are seeing now, her wandering around smelling, is common after a seizure. They are disoriented for awhile afterwards.
Lady has been an epileptic for nine years. This website has been my "bible":
Canine epilepsy and diseases that cause seizures in dogs