I don't think an audit would help things, unless you really think they are stealing funds.
Talking with the principal would help, as well as reviewing Robert's Rules and making sure the president runs the meeting -- not letting the treasurer dominate/make up the agenda.
Our principal comes (and is invited) to our board and general meetings, so he would be able to back up the president, if someone were trying to take over or claim that decisions had been made at a different meeting where the president and principal were not present.
Parent organizations in the school exist at the pleasure of the principal and the school district.
Because your friend feels like she's being shut-out of the organization and decision making, she needs to enlist the help of the school principal. An audit needs to be done on the organization's books (ask the district to demand it) and a review of the by-laws and procedures.
Your friend won't be able to solve this complex issue on her own, but should make great strides with partners like the school administration in her corner.
My friend is a PTO pres and she is having a real bad time. The Treasurer is running the meetings instead of letting the Pres. do it. She is just making decesions instead of voting. They hold secret meetings without her. They are bullying her into quiting. The only thing that she has done is question the limits they are trying to set on spending for kids. They are more interested in having business lunches (without her) and making decesions that the treasurer wants to go through. Things just seem to secret and dishonest and my friend is feeling that they are not working for the kids. They are just doing fundraiser after fund raiser. Back to back. We live in a small town (not city) and the comunnity is stessing on the continuous efforts. They are temporarily tapped out. She doesn't know what to do. She wants to quit. She doesn't feel it is for the kids anymore.