Car seat safety is important but I agree there is something more going on here. Op, you seem dissatisfied with your nanny's literacy/language skills. The issue will come up again in some other way. It's not your nanny's fault if you hired her knowing English was not her first language. You must have weighed your priorities to decide on this person over other candidates. Now you need to take responsibility for your choice or hire someone else.

OP, ignore all the rude people here. Car seat safety is important, but not everyone believes so.

Go on Safekids.org and find a certifiied technician who speaks Spanish. Set up a time for that person to come and teach your nanny how to correctly install the car seat. Make sure you stress to the nanny how important a correct install is.

Alternatively you could get one of the new Britax convertibles with Clicktight technology. Both the Advocate and Boulevard will last a lot longer rear facing and forward facing than any of the current Britax seats.