Most likely, her account tripped an abuse detection system. Of course, WhatsApp is not going to disclose how the system works (not even to disclose which factor

Most likely, her account tripped an abuse detection system. Of course, WhatsApp is not going to disclose how the system works (not even to disclose which factors were used to make the decision), because that will allow abusers to more easily circumvent it. Heaven knows there are enough spammers using WhatsApp. If it’s worth that much to you, hire an attorney to send a letter demanding an explanation and restoration of service. You’d be surprised what can happen when a company’s legal team gets wind of a problem.