How late can my commuter flight be to still make my main flight?

[disneysnowflake]

We're traveling with United.
We're now leaving at 6:25am from a little regional airport for a commuter flight to Dulles.
I spoke to a worker at this little airport who informed me that in the Winter it is very rare for flights to take off on time from this little airport because they only have room to de-ice a plane one at a time.
She said that between 6am and 6:30am four planes are scheduled to take off. Our 6:25am flight is last to take off.

If we leave on time our commuter is set to land in Dulles at 7:25am.
We are to leave Dulles for Orlando at 8:25am on Ted.

How late can our plane be in arriving in Dulles for us to make our flight out to Orlando?

I don't travel very much. I'm really worried because the gal at United told me if we're late for our 8:25 departure from Dulles we won't get another flight out of Dulles until late afternoon or early evening. Ugh.

 

[safetymom]

They will board you up to 10 mins before departure. Also usually the flight times allow for some delay so you could be delayed and still arrive on time.