I know of no requirement for you to be provided a rehab transfer based on the information you’ve provided. If your unit is considering separation, then the provisions of AR 635-200 might apply. Please see below.
In some cases it is appropriate to transfer a Soldier to give them a fresh start. This can usually be done once an Article 15 has entered the punishment phase. Sometimes the chain of command may believe the Soldier will be better served by staying in their current unit. In addition in some cases it may be difficult for a unit to execute a transfer because the Soldier may be in a low density MOS or the unit does not have a sister unit close by to execute the transfer (this usually applies to overseas locations).
My recommendation would be to prepare a written statement to the commander who executed the Article 15 and formally ask for the transfer. Ensure your statement is calm, void of emotion, and contains the facts and reasons you believe the transfer would be the best course of action for the you and the current unit.
c. Rehabilitation. Except as provided in d, below, the following rehabilitative measures are required prior to initiating separation proceedings for entry-level performance and conduct (see chap 11), unsatisfactory performance (see chap 13), or minor disciplinary infractions/patterns of misconduct (see chap 14):