my sister is in love with a married man!

This is common issue now a days. Within one year any relation break up and new one starts. This is continueous process. Where there is flirt in any relation, will end up soon. No stability will be there. Seems this is first relation of your sister. She should have chosen fresh one. Why she is developing relation with married man, I cannot understand. If she is also married then no problem. But suggest her to start such relation with fresh boy. married man can leave her after some time as he is leaving his present wife and coming close to your sister. Try to understand her with the help of your friends and family members not to go ahead in this relationship. This may end up soon. There is little chance of stability.

It's just too bad for her. Those kind of men never leave their wives, he'll just make her suffer a lot. How about therapy? Will she listen to a professional? Someone should make her realise she deserves better!!!

This is really very tricky situation but the only solution is to take her out from this relationship as there is no future and ahe cant ruin the other relationship unintentionally. Well i feel you should take her out from that place for some day and explain her feelings will take her nowhere but to depression.i hope my advice works and all the best..