My sister has a history of datin losers?

OK, so my sister who is 21 always dates jobless losers, they always have some blah blah excuse as to why they have not found a job. Well in the past I have been very blunt with her, always telling her what losers they were and such. but it started to cause her to build resentment towards me! And she and I are very close, she is my besty and my sis! we have always been attached at the hip. Any how this new bo she is with (5months now) I have been nice(ish) to and told her I like (ha ha yeah no) he has the same story, no job blah blah reasons for it, and it is driving me INSANE!!! I have kinda told her my thoughts but am really trying to keep hush on this! WHAT do I do, should I keep sittin back watching her fall far YET another loser or should I say somethin! HELP! and if I should say somethin what should I say!