When the blue line is level to the ground that represents the mid-point of the recline range. You can recline the seat further and that should fix the chin-to-chest issue. It's not really a safety risk at this age, but given that you can increase the recline further and the head-droop is bothering you, I'd just increase the recline. Britax allows the seat to be installed as reclined as 45* when measured from vertical. Sometimes just a degree or two will make a difference.
If the seat was reclined all the way I'd tell you to not worry about it - and honestly, I wouldn't worry about it - but since you are able to recline it further while keeping it within the allowed range, I'd try that as sometimes just a few degrees of recline can make all the difference in the world.
Also check that her bum is scooted all the way back when you buckle her in - sometimes if a child is slumping in the seat it can lead to their head falling forward.