Considering that Axis Sally was convicted of treason after WWII and out in 7 years, it is something to consider.
You seem to have a basic misunderstanding of the penalties handed out to Americans who steal classified information and give it to someone else. It has nothing to do with who receives the information and more to do with the importance of the information itself. Pollard received a life sentence because of what information was compromised. According to a classified memorandum written for the trial judge by then-Secretary of Defense Caspar Weinberger, Pollards actions amounted to treason. It is difficult for me to conceive of a greater harm to national security, Weinberger wrote.
We have had others who have spied on behalf of Israel, e.g., Larry Franklin, who were not sentenced to life. And there have been other spies like Aldrich Ames and John Walker who received life sentences. To suggest that Pollard was unfairly singled out in terms of punishment is nonsense. Why do you believe that to be the case?