
Hi Cor,
How strange you have an ID but posting on the Visitor's forum

Anyway, to your query - at 13 weeks this is normal puppy behaviour regardless of breed - puppies explore everything with their mouths and chewing is particularly exciting ;)
Try this
LINK - follow the steps religiously and ensure consistency throughout with all family members, visitors, etc.
Of equal importance - please remember that your puppy is very much a baby still and has no idea what you are asking of her - you have to train her to behave appropriately which requires great patience and the ability to ignore naughty antics and lavish praise on the things she gets right.
Regards, Teri :)