Most Helpful Girl
When it comes to taking a break in a relationship, you should always set some ground rules so you are both aware of them. Generally speaking in a break having sex with someone else is something expected to happen during the break.
Most Helpful Guy
There is no break, you're either together or you're not. When you break for any length of time you are single. Hence she can do what she wants. If you had a solid relationship then you wouldn't need a break in the first place.