1. Yes, you have a case against her for non-competition, non-disclosure, non-solicitation as per the clauses mentioned in the Contract she had executed with you (5 years after termination),
2. She has published her joining your competitor for which several clients informed that they will follow her. This is enough evidence of her solicitation by joining your competitor,
3. You shall have to evaluate your loss of revenue for the absence of your earlier clients who are not comiing to you now and then extrapolate it for at least a decade to calculate the total damage,
4. It will not be prudent on your part to pursue the case hyourself with out an attorney who has specialisation in the subject,
5. First let you have the decree of payment of damage after which you can pray for the suitable method to realise it from her.