I recommend one! Mine is so used now I wont ever bother getting one. But I'm sure it would help tons. I have dust and stuff that gets built up in the corners of the screen thats super annoying to clean out. Might also deflect scratching or other possible damages.

Sora No Otoshimono, Mitsudomoe or Clannad.

If she can go behind her fiance's back to see you she is not worth your time in my opinion. If she does that to someone she's supposed to marry then she has the potential to do the same to you. She held back letting you know she had one in the first place, the whole situation just seems wrong and i'm sure you can do better than someone who obviously is sneaky.

But anyways, to answer your question, if you can steal someone elses bf/gf then that person obviously doesnt want to be with that person anyways. I don't think it is right to try and seduce someone away but in your situation it's her leading you on. She's in the wrong and it's your decision whether or not to get involved with her. You're technically not stealing her, she obviously doesnt want her fiance if she wants to meet you again and says she still likes you.