as salam alaikum
if the wife observes her husband's conjugal rights and he is financially able to provide for her, she should try to convince him with good advice and persuade him to rectify his conduct. If he is not willing to do that, she can involve other people that she thinks may have influence on him (like relatives and friends). If this also doesn't work she may refer to an Islamic Judge who should decide the best reconciliatory course to the matter. Then, if he sees that there is no better option available, he may divorce them at wife's request.
With prayers for your success.