• Drug conspiracies are frighteningly easy cases for the government to win.  A "conspiracy" is an agreement to commit an illegal act.  In drug cases there is no requirement that the agreement be carried out or for any act to occur other than the agreement.  Typically the government tries to show that two or more people were cooperating to distribute drugs.  The cooperation can be proved through circumstantial evidence.  The government likes to charge conspiracies because you do not have to have drug seizures or witnesses to drug sales.  A single witness who can testify that there was an agreement is sufficient for a conviction if the jury believes the witness.
• The penalties for non-violent drug offenders are out-of-whack.  There is nothing your attorney can do about this bleak situation.  We have elected lots of representatives whose promised to be "tough on crime."  No one seems to recognize the injustice of these sentences until a friend or family member is facing one.  There is at least one group seeking change.  The harsh penalties are a fact of life in your case.
• Trial vs. plea.  Every accused faces this choice.  The nearly universal rule is that an accused who pleads guilty will be treated more leniently than one who is convicted after a trial.  In advising a client on what to do I discuss the "upside potential" versus the "downside risk."  The "upside potential" is the likelihood of being found not guilty, the downside risk the the likelihood of being found guilty and being treated more harshly than if you had plead guilty.  The greater the chance of a not guilty verdict, the less incentive there is to plead guilty.  If the government has a slam dunk case, it will usually be best to take the plea.

I hope this has helped some.  The best advice I can give you is to consider your attorney's advice very carefully.

• Hostile work environment:  You used the term "hostile work environment" (HWE) in the subject of your e-mail.  An HWE occurs when an employer allows or tolerates harassment based on gender, race, color, national origin, age or disability.  This would include tolerating employees who request sexual favors from other employees and same-sex harassment.  For example if a supervisor has a relationship with a subordinate, that could form the basis of a claim of HWE because other employees may believe that going along with the advances of a supervisor would help their careers.  This is sometimes called "quid pro quo" discrimination.  A careful employer should prohibit sexual relationships between employees and supervisors.
• Check your state laws: My answer is based on federal and North Carolina law.  North Carolina law places few restrictions employers.  It seems unlikely that any state would require employers to halt consensual sexual relationships between employees who do not supervise each other, but you never know.
• Telling the lovers to knock it off:  The employer has no legal responsibility to stop the affair unless it has a tendency to create a HWE.  While there are some very creative litigators, I don't see how an affair between employees in different departments is likely to create a hostile work environment.
• Employment policies:  I don't know how large your company is but you could consider developing a set of employee manual that sets clear guidelines of what is and is not allowed as far as relationships among employees.  If you have clear policies and enforce them consistently, it can help in the event an employee brings a claim.

The EEOC has a Q&A on employment discrimination.