Sounds like she's looking for an excuse to bike; GREAT! Why don't you take the 15 mile route that you feel comfortable with, and when you're running late, go over the interstate?

It doesn't look like you're going on the expressway, just crossing over the bridge that spans it. Just be alert when you do and look for the safest route, like akohekohe suggested.

Did you decide what to do with regards to the bike yet?