Do a tag search for jealousy. There has been a lot written here about it because it is such a common problem in polyamory and even more so in a polymono relationship. My advice is to try and deconstruct it and work out what you're really feeling. Jealousy as a label for emotions can cover so much. Are you insecure for example, that she might develop a more intimate relationship with this guy and it will affect your relationship. Or maybe you are just plain lonely when she is away on her dance trips and you feel the inequity of being alone when she is quite possibly in someone else's arms? Maybe you're upset that she doesn't seem to place much validity on your feelings? You asked for tips and deconstruction of the term "jealousy", as it applies to your relationship, would be my top tip.