In South Africa, the capacity of a married woman to contract is governed by the Marriage Act 25 of 1961. According to this act, a married woman has the capacity to contract as a legal person in her own right, independent of her husband. This means that Gin, as a married woman, has the legal capacity to enter into contracts and transactions without her husband's consent.
Therefore, Tonic's purchase of the flat from Dash without Gin's consent does not necessarily invalidate the contract. Gin has the capacity to enter into contracts independently, and Tonic's failure to pay the purchase price does not release him from his obligation to fulfill the terms of the contract.
However, it is important to note that Gin may have legal recourse against Tonic for entering into a contract without her consent, depending on the specific circumstances of the transaction and any applicable laws in South Africa.
In terms of advising Dash, it is important to clarify whether Gin was aware of the transaction and whether she gave her tacit consent. If Gin did not consent to the transaction and was not aware of it, Dash may still be able to enforce the contract against Tonic, but Gin may have legal grounds to challenge the transaction based on her lack of consent.
In conclusion, while Gin has the capacity to contract independently as a married woman, the specific circumstances of the transaction and any potential lack of consent on her part may impact the enforceability of the contract between Tonic and Dash. Both Tonic and Dash should seek legal advice to fully understand their rights and obligations in this situation.