sis i woudnt call that little dog a crested but she is cute lol
in terms of breeds...
a yorkie is HIGHLY likley to break the 6-8lbs barrier, unless she buys a "teacup" and since those are just runts/sickly from bad breeders because teacups dont exist its NOT a good idea unless she wants to be huffing something a little larger in her purse.
my biggest concern with the yorkie is the potential to be incredibly barky little dogs.
a chihuahua might be a good choice...
while they are "known" for being hard to house break, its simply a case of not taking them out enough to start with....they simply cant hold it as long as a larger breed and need to be taken out every 1/2 hour at first with persistency they can be house broken. they are very inteligent. have a good energy level (they CAN get enough excersize runing round the house but enjoy a good walk too...)
they are the right size (with a chi bred to standard being anything from 3-6lbs...(again do not buy teacups (which usually end up in the 3-6lbs range anyway and watch for byb's)
barking can be an issue with chis but ive found the squirt bottle and "quiet" command to be wonderfull training tools. my chis bark ONCE if the door bell rings then i give the "quiet" command and thats it...all stop. it took about 2 weeks to get all 3 behaving...but it worked and woudl be mush easier if trained from the get go.
they come in long and short hair and while its not a "Hair" they are both considered Low shedding dogs and coat upkeep is VERY simple. (long haireds tend to shed less than short even, and there usually good with allergy sufferes too)
a chi however MUST be well socilized, and allowed to be a dog once in a while, theres nothign wrong with carrying any dog round for some of the time but they ALL need to be allowed to walk and get dirty too, this is particularly true for chis who tend to be owner posessive/protective particularly when carried around all the time.
Toy Poodle:
again, expect them a little larger on the weight scale than the 5lbs, while there are some very small toys out there watch out for "teacups" "tiny toys" "pocket" ect.
very smart...
more grooming upkeep than the chi but shed even less!
Chinese crested: Powderpuff
great breed, they tend to be a little bigger than shes looking for, a cresti in the 5-8 lb range is considered VERY small with 8-12lbs being the common average...
the powderpuff is fully coated (though theres nothing wrong with the hairless either but i understand not to everyones taste)
however they have HAIR not fur (though it can vary from a silkie human feeling hair coat to a wooly lambs wool feeling coat neither types are shedders, this breed is considered "hypoalergenic" like poodles, even when fully coated.
they do require frequent grooming, but not as intense as the poodle. puffers can be clipped, full coat requires alot of upkeep.
cresties can be talkers but are not prone to BARKING, instead making a combination or yolws, grumbles and occasioan short yips...they CAN bark and some do like to hear their own voice, but there also very sensitive and if they know it bothers their person they generally stop. (quite works well for these guys too)
they are inteligent but can be aloof with those other than thier people...
(ie, if dad tells ruby to sit she will look at him...then look at me...and WAIT...if i confirm the sit she will (or if he has food lol) however if i dont she just kind of gives him the "why?" look.
cresties LOVE to run and while will be ok in an apartment will need a good playtime and walking...
powderpuffs dont have the skin issues or dental problems that the hairless do.
leave natural faced for a terrier look or have the face shaved for a more "refined" look.
cresties, even powderpuffs require protection from the elements, lighter dogs are particularly prone to burning, and should wear sunscreen, and t-shirts in the summer and coats/sweaters during the winter.
most cresties are allergic to wool...
if she likes the hairless a hairless would be perfect, absolutly no shedding there lol.
Pappillion
other than the potential for energy level a smaller pap might be perfect.
maltese and shitzu are also potentials but tend to be alrger than her desired weight bracket.