I completely agree with 1) that this can be difficult and I wish you weren't in this position; and 2) you should contact the police.
There are myriad reasons why the trained professional is the best person to take the next steps. Going to the police does not mean your friend/colleague is going to have the SWAT team breaking down her doors. Nor does it even mean that there will ever be any charges or public mess (though there could be). The first steps will be questions and looking in the right places by a professional. And that's what should happen. Us amateurs wouldn't know the right questions to ask, how to ask them or where to look correctly.
I also feel like it's close to a fiduciary responsibility of yours as a leader to take the necessary steps to recover thse funds.
Please be careful if you talk to her you don't want to accidentally violate the law yourself. If you were to say to her "Do _________ or I will call the police." That is a crime so it might be better off to let the police handle it from here.
See the thread entitled "Missing Funds" by Mom21. You can find it on the "Top Message Board Requests" forum below this one. She had to lead the charge against a PTO member who had embezzled funds and is at the stage where the trial is coming soon. You may find some helpful information there.
This is so hard; I'm sorry you are having to deal with it. However, the embezzlement is a crime. You need to go to the police and work with one of their detectives and the prosecutor's office. They will tell you what to do.
Be as discreet as possible. Everyone is innocent until proven guilty. It might even be that you "know" she's guilty but it isn't possible to prove so legally. Then you put your own selves at risk if it appears she's been slandered but is legally innocent. Not to mention there most likely are innocent children in the midst of all this.
I'm not saying to sweep it under the carpet. Just contact your local officials and proceed cautiously.
As the president of our schools PTO it has recently come to my attention that our treasurer has been stealing money from our PTO to the sum of about $5,000. I have discussed this with our co-pres as well as the school principal. As much as we don't want to believe that this has happened, it has and we are not sure what our next step is. We are thinking that we are going to confront her with our findings and hope that she comes clean with us and pays back the money. My question is, should we try to get her to confess or should we contact the police at this point and what evidenance do we need to show the police. If we do contact the police, will she be arrested right away and how much involvement will I have in the prosecution. If you have a similar story, I would love to hear what happened after you discovered that someone was stealing money from your organization.