Per definition the maximal lift generatable at the Kármán line is
$$L = m \cdot g$$
so if your body is generating significant lift at sea level it will probably still generate enough lift at that altitude to divert from a "vis-viva orbit" after a short while. The bigger problem however is drag. To quote Wikipedia:
Due to atmospheric drag, the lowest altitude at which an object in a circular orbit can complete at least one full revolution without propulsion is approximately 150 km (93 mi), whereas an object can maintain an elliptical orbit with perigee as low as about 130 km (81 mi) without propulsion.
So simplifying the orbit to have no other forces, as the vis-viva equation states, specifically to be a frictionless one would be a gross misstatement.
In general during deorbit of a spacecraft the altitude around the Kármán line is considered part of the reentry.
(Image Credit: Comparison of lifting reentry and ballistic reentry by A. Rathan Babu, P. Vijay Kumar, B. Praveen, and R. Suresh Kumar)
As you can see in the graphic:
- There is a measurable deceleration for a reentering spacecraft at that altitude
- The friction depends on the shape, size and orientation of the object
Spy satellites or earth observation satellites orbiting at similarly low altitude usually have a propulsion system firing permanently or quite frequently to keep the orbit and are built to be very aerodynamic to minimize friction.
There is enough friction at that altitude to make the vis-viva equation not applicable for even short term orbit calculation.