Duplicating is prohibited, according to Stardoll's One-Stop Rules. Your account will get warned/possibly terminated if caught duplicating. However, there are workarounds:
- Only duplicate on accounts you know you can risk. From this account, you can either sell/gift the duplicated designs to your primary account safely, however, you have to make sure that you do not make it obvious that the secondary account is yours.
- Never connect the same email address, Facebook/Google+/Twitter login, etc. between your secondary and primary accounts.
- Always be careful and copy wisely.
Remember that you should copy at your own risk.