A husband getting married to a second wife is not grounds for divorce for the first wife.
In the event a woman has a valid reason for seeking divorce she may offer the husband 'khula'; a monetary settlement which usually involves the wife returning the amount given to her as mahr or any amount demanded by the husband. If the husband refuses to accept the settlement the woman may go to a shariah council who after investigating the matter will try to resolve the matter amicably and at times as a last resort grant the woman, with a valid case, a forced divorce if the husband is adamant.
