When I went to see Jake he could fit in my hand and could have easily fitted in a cup.
He is now a big lad for a Chi and weighs 3.45kg (7.6lb). So just because they look small at first don't mean they will stay small.
Not trying to put you off but if your looking for a small Chi or at standard weight at the most then I'd be asking the breeders what the parents weighed.
I noticed that this pup has big paws just like Jake. As you say your just looking for a pet and your happy with what the breeders says the go for her, she is gorgeous.
Bear in mind ask for a vet health certificate, I have just found out today that Jake has to have operations for both knees for Luxation Patella.
Just another thing to consider and no disregard to the breeder but IMO a good breeder with good dogs does not need to advertise on websites such as preloved nor show the puppy in a cup.
I bought Jake from an internet advert and I don't regret for one moment buying him. So if this little girl is what you want, go for it..