A re-entry permit is not going to make that easier. In fact, they would only be able to give it to her valid up until the date of the expiration of the 2 year green card. Besides, a re-entry permit is for a long trip abroad, not for short trips abroad.
If she is already divorced, I would not recommend traveling. Keep in mind that Lawful Permanent Residency is for someone that is residing in the U.S., not for someone that is just taking brief trips into the U.S. from time to time. You are not saying that she is doing that, but still, I don't recommend traveling.
They are getting tighter and tighter with these things and it will be harder and harder for her to keep doing what she is doing.
IF they were to find out that she is divorced, she may have some very big problems trying to come back in because technically, her residency status is terminated.
She must file the I-751 waiver application ASAP to keep her from being put into removal proceedings. Unfortunately, the I-751 waiver will probably take awhile to process and during that time, I do not recommend that she travel because as I said, the conditional residency is technically terminated by the divorce.
So it is a HUGE risk for her to travel. I do not advise it at all.