Did my boss do the wring thing?

It is wrong. Your friend/boss is claiming credit for a service his business is not able to provide (misleading his customer) and is taking repeat business from your sister. She's probably kept her mouth closed to protect you rather than yor boss but even so he should not have put her in this position. She should speak to him about it privately or just slip her own business card into an invoice or piece of work for the customer.