Letter From Ada

Once a Plaga egg hatches, it's nearly impossible to remove it from the body. But if it's before it hatches, then it can be neutralized by medication.

If it does hatch you might be able to get it out by surgery before it turns to an adult. But it won't be easy. There's a high chance you won't survive the operation.

As far as I know the girl was injected with the egg before you. Her time is ticking. You should prepare yourself for the worst case scenario.