An AK-47's bullet has an impact force of 2045 Joules.

It's not really specified how many shots (or what type of bullets) her shield is redirecting. If she can absorb a whole clip of AK rounds, that would equate to her absorbing ~61,350 Joules.

Which is about the force of you being hit by a car moving 150mph (which hits with 60,968.9916 Joules) based on my napkin calc.