That's the deal.
If you both agreed that dating other people was okay, there is nothing you can do but accept that that she does whatever she wants.
Now, being in this type of open relationship or love triangle situations is extra challenging.
Most people can't and don't want to take it.
This is why they decide to go for a committed relationship instead.
Now, if it's a situation you want to maintain with this girlfriend, here are a couple of ideas you can strengthen.
Any time you feel jealousy coming to the surface, reason yourself and go back to ideas like:
"She is free"
"She does what she wants"
"I have no right to tell her what to do!"
"This is what we agreed in the first place"
That's the first step. You need to create a new mind set and emotional reactions for the exact challenge you face.
This implies reconditioning (don't be scared! It's a good thing) yourself to respond differently.
It's something that can easily be learned within a week.
I know I just triggered your curiosity, right?
Here is your next step:
http://vitalcoaching.com/malejealousy.htm
Get this e-book and MP3 audios. The e-book is around 100 pages of pure dynamite focused on mastering your jealousy weapon and shows you how to do exactly what I described.
Your goal is to use your jealousy if and when you want it.
This is what I will be honored to teach you.
Get it now!
http://vitalcoaching.com/malejealousy.htm
To you!
vitalcoach