Does the exchange between two female friends regarding their sins, with the intention of seeking benefit, advice, and prayer, fall under the category of openly committing a sin?

The basic principle is that whoever is afflicted with a sin should conceal himself and not inform anyone about it, lest it be considered blameworthy open disclosure. This is unless there is a benefit in disclosing it, such as seeking a fatwa or advice. It is preferable for whoever asks about his sin to phrase the question as if it were about someone else.