Deliberate mistake: When Selene and Michael are driving a truck, chased by Marcus, at one point in the chase Marcus flies directly ahead of the truck and stays upright in the air with wings outstretched, facing the truck. Given that the truck is travelling at high speed and Marcus is using wings for flying, it is just not possible. It can't be attributed to Marcus' inertia - he stays in front of the truck for a couple of seconds, long enough to lose any speed advantage he had before.
Deliberate mistake: When Marcus attacks the Truck, all the windows get smashed. Michael climbs back in and starts a conversation with Selene. There seems to be hardly any wind, although they're driving at quite a speed without a front window. They both have long hair, it should move.
Answer: This could be a confusion over characters. If I remember rightly, the film opens with a scene set somewhere around 1200AD, showing the three vampire elders, Markus, Viktor and Amelia, leading a war party. Possibly your friend has mistaken Amelia, played by Hungarian actress Zita Görög, for Selene, who doesn't appear in the film until after this lengthy flashback sequence has finished.
Tailkinker ★