IF the consultant had a non-disclosure or confidentiality clause in the agreement which required her to not disclose this information, you could sue her for breach of contract. However, unless there was some contractual obligation to not disclose this, she could: people (and businesses) may disclose information except to the extent they agree to not do so. If you have not done so already, in the future, make sure all consultants and contractors sign confidentiality, etc. agreements.