Can two people ride on a Honda Rebel 250?

I weigh 200 lbs. And my girlfriend weighs 135 lbs. Will the bike be able to go at least 60 mph? The rebel is a 1985.

Yep. My first bike was a 250 Rebel. I was a little heavyset back then and I rode with passengers all the time. You'll feel the difference in power, but it'll still go about 65 on the highway.

If it has two seating positions and two sets of footpegs, you can take a passenger.

The bike will start to struggle at higher speed with two people on board, but it should be able to attain 65mph in most conditions. You will have more trouble at high altitude and if you are encountering strong headwinds.

The weight of the pillion will make the acceleration a bit slower.
Your passenger does not cause any extra wind drag, so your top speed will be the same with or without the pillion.

My Vespa LX150 has 11.7 bhp and can touch 68 mph, cruise comfortably at 60.
A Rebel 250 has 16.1 bhp and will do 75+ mph actual (80+ indicated) and cruise an actual 65+ mph on the Interstate (over 70 mph indicated.)