How large is the radar cross section of an F-22 Raptor and how does it compare to other, similar jets

As large as other similar sized aircraft with similar profiles.

She is correct, but only if they are made of the same materials and finishes as well.

But that really did not answer your question, and l do not believe anyone in this arena can.

That information is classified but some 'experts' have claimed that it appears on radar as gound clutter or a small flock of birds.

l have no idea and l have worked on it. Rumors have it as smaller than a pea. l would assume so because even an F-16 has one only about the size of a golf ball. Stealth is only part of the F-22. It is an awesome fighter. The best in the world and capabilities are still being added..Like a lot of things about it , classified.

The actual numbers and limfacs are Secret/Special Access Required. This is a generalization, as different radars have differing reflectivity but it is very small.
Stealth is not a panacea, bi-static radars (which have non-axial transmitters and receivers) can track low-observable aircraft. Stealth works by giving the crew that few extra minutes to deliver their ordnance and get out.