Marked By My Mates by Skye Alder

Birk and Heath have always been inseparable.
Then Ivy moves to town.
Now they’ve got bigger problems than graduating and finding their place in the pack.
They need to figure out how to tell Ivy about shifters and wait until she comes of age so that they can see if she’s the fated mate to either of them.
When Ivy and Heath go hiking one day and she falls and hurts herself, badly, he has a decision to make.
Hope that she can survive the trip back to town, or bite her, forcing a mating but saving her life in the process.
The decision is easy.
Living with the repercussions when it turns out that Birk was her fated mate is a lot harder.
Will their friendship be able to survive when they learn that they have to share their mate?