show some sympathy for the guy unless he did somthing wrong
You don't. If she hasn't told you she is in an open relationship that this is most likely not interested.
You should snog your boyfriend if you are a little deep in your relationship.
If a girl has dumped her boyfriend, he should be aware of it. If he has not "figured it out" then she did not communicate the fact that she no longer wishes to pursue a romantic relationship with him and she should do so. Since you are now seeing this girl, you should ask why she would not clearly communicate this to him. This could indicate that she is afraid of confrontations and would even lie to avoid them, or that she is not ready to burn that bridge with her ex-boyfriend as she might go back to him. It could even mean that she is someone who is not truly interested in either of you but is instead interested in getting attention. In any case, you should speak to her directly about it. If you see her ex-boyfriend, you should definitely not discuss this with him because his relationship with your current girlfriend is not your business. Discussions about their relationship should only be made with the person you have a relationship with (the girl in question).
You should really take sometime away from your current boyfriend to decide what it is you really want especially if your interested in someone else. Take some time to be on your own to sort out your feelings.
You should talk to him about this and tell him that you're not interested, and if you are, I wouldn't recommended with it because that would be quite bad if you ruined you and your friends relationship over a mere boy.
If your crush has a boyfriend then you are not her crush. There is no relationship, you are just a friend.
If you want to end the relationship, just let him know that you're no longer interested hi and that way and that the two of you should break up and see other people.
Start looking for a new boyfriend.
This will depend on how you feel. If you want to stay with your boyfriend explain to your friend that you are in a relationship and you are not interested in him more than a friend. If you have feelings for your friend you will have to leave your boyfriend but don't jump into another relationship right away date and see how things go - but remember if you change your mind the odds are your boyfriend will not take you back so make your decision wisely. If you are just undecided and have feelings for both you should not be a relationship at all - you need to be single to take time and sort out your feelings and don't rush into a relationship with anyone.
IF YOU HAD A GOOD RELATIONSHIP BEFORE.
Involve your parents.
No