Petito/Schmidt attorney Pat Reilly stated the contents of the letter to Brian Laundrie are "pretty extreme."
Could be, but we also know that the P's attorney has used this "extreme" type of rhetoiric often, desribing the L's behavior as extreme or outrageous because they didn't respond to phone calls from the Petito's, that they blocked their numbers on their phones, that they had a long weekend camping trip (even though it had been planned long before BL returned home), etc. So until we see for ourselves the content of the letter between RL and BL, his description isn't entirely credible.
The most specfic he is willing to be about the contents of the letter from RL is that it contains "an offer that had to do with Gabby." But he does state that he doesn't know when the letter was written. He says he is requesting a copy in relation to the civil lawsuit against the Laundries.
If it was written before GP and BL set out for their cross country trip in the van, as the L's lawyer stated, then it could have been advice to BL on how to deal with difficult situations that could transpire during the trip, including difficulties in their relationship (GP and BL relationship) in such tight quarters and on such a long trip. That's another possibility.