I applied for registration as a British citizen last year, and it took about 4 months from start (sent off application) to finish (received certificate of registration). I'm assuming your wife is applying for registration based on her mother being born in England? Was there anything unusual about her application? I'm a bit surprised that it is taking this long as the IND website is indicating it is taking on average less than 2 months for adult registrations.
When I had a question about the status of my application, I used the following email address:
nationalityenquiries@ind.homeoffice.gsi.gov.uk
I quoted my reference number, which was on the letter I received from the consulate when I got my passport, mother's passport, etc. back. It took a few days, but they did reply to tell me that my application had been approved and sent to the consulate in LA. Sure enough, got a phone call from the consulate 2 days later asking me to set up an appointment for my 'oath of allegiance'.