In Congress Instead Of In Jail?

A member of Congress was caught working with (suspected) foreign espionage agents,

According to three former national security officials, Harman was heard promising the suspected Israeli agent that she would intervene with the Bush administration to try to get the espionage charges against the AIPAC officials reduced to lesser felonies.
The suspected Israeli agent in exchange promised to lobby Pelosi to give Harman the chairmanship of the Intelligence committee if the Democrats took control of Congress after the 2006 elections.

Why hasn’t this member of Congress been prosecuted? She was caught in a quid-pro-quo with foreign agents, who were attempting to plant a compromised person into a high position where she could pass intelligence to them.
Yes, I know. The story came out that the Bush administration blackmailed her into supporting their policies or they would reveal what she was caught doing. Fine, but that was then.
Now that we know the story, should she be prosecuted? Obviously she needs to resign her seat, but my question is why isn’t she being prosecuted?
We seem to have a two-tiered system of laws now, where some crimes are prosecuted, some are not, some countries are allowed to spy on us and get away with it when caught and others are not, and the President gets to decide which laws will be enforced and which will not.