Tsuji was irresponsible, she knew about the risks she had while having a sexually active relationship, so it was entirely her fault (she had influences by kago and yaguchi, but she has to respond for her own acts).
If you're condoning her behavior, it may show you're not responsible as well and could always have trouble at work, cause you do what "you feel at the moment" forgetting about your duties. So maybe the rules are to strict, and are likely to be broken, but it's still a rule, so if you break it, you must pay the consecuences. That's being an adult, some of you will learn it someday...
Anyway, at least she didn't behave as bad as kago did (who is much more immature), as reported it was a mutual decision, she's taking the responsability of raising the child, getting married (that's a choice, not a need) and leaving her job.
I hope she can happily raise her child and be happy.
And I hope that not one of the girls follows her footsteps. They were already two recent bad examples for the H!P members and for the general public as well, they are idols, so they are a public role model, you're showing an image, and that's your work. If you fail to do that, then you're not doing your job right, if you don't want to keep doing it, then just quit your job in a proper manner.