Not Psylocke.
Yes, she is rendered immune to reality warping with regards to her own being/body.
BUT she can be killed in the more conventional ways, as Jamie stated. Death by headshot, decapitation, suffocation, etc. And reality warping can do that, kill her indirectly. For example, alter the environment into a fatal one: create a room of Adamantium around her without any air inside suffocating her; have bullets come from all directions possible at insane speeds; turn the air into fatal poison gases. Psylocke's RW defense doesn't extend outside her own person. Reality warpers can indirectly kill Psylocke in a variety of ways.
In addition, her "alterations" by Jamie -- immune to reality warping and telepathy -- aren't absolute, at least with the latter. Two characters, implied to be cosmics, were able to read Psylocke's mind despite Jamie altering it to be unreadable.