Okay, who wants to settle

Okay, who wants to settle a grammar argument? My wife, Holly, and I disagree over this paragraph from the contact us page of the brand new web site that her employer just launched:

As you've toured our site, you've seen many examples of how the staff at Hellman Associates has helped our clients formulate their business goals and implement innovative marketing tools to achieve great results.

Now, I say that it should read "how the staff at Hellman Associates HAVE helped our clients", because staff is a plural noun, and you wouldn't say "The people at Hellman has helped me a lot!", at least not if you had all your teeth, or graduated from high school.

She says "No, actually, it depends on how you use plural nouns. This is acceptable usage, as we are working together as a single entity (in theory)."

So who is correct? Post your comments below!