The diabetic's blood sugar will most likely spike higher and take longer to return to normal.
You have several different types of insulin response. Your first phase releases stored insulin very quickly after eating so that your blood sugar never goes too high. In other words, the spike is blunted.
Your second phase is real-time insulin production, so while it takes longer to get released, it eventually does and takes up any remaining glucose that the first phase didn't get.
In a person with Type 2 diabetes, not only is there insulin resistance, but the signaling to the pancreas from the gut is impaired. Usually the first phase deteriorates first, so a person in the early stages of diabetes might (without knowing it often) spike very high for brief periods of time after a meal. The second phase eventually kicks in and rebounds blood sugar, but the initial spike is the early warning sign that the glucose metabolism isn't working well. Eventually the second phase deteriorates, too, and so blood sugar takes longer and longer to return to normal.
A person without any kind of impairment will usually not see much of a spike, and may never even cross 100 mg/dL. Blood sugar will also return to normal really quickly, often around 1-2 hours. Once the first phase insulin response disappears and the second phase starts laboring, blood sugar can take hours and hours (or days) to ever return to baseline or fasting levels. That's why it's important for a Type 2 diabetic to not eat foods that raise blood sugar too much. There won't be much first phase insulin response left to soften that spike and the second phase, while working, won't work as well as it would in a non-diabetic. I can stay below 100 mg/dL the entire time after a meal simply by not eating anything that would raise me over that in the first place. If I do eat foods that cause more of a spike, I won't be back to baseline within 2 hours.