Yes. There is nothing wrong with a part time exempt. If the job qualifies as exempt for a full time, it will still qualify as exempt for a part time.
I recently had an exempt employee come to me and request that she be able to cut her hours in half to 20 per week. We cut her salary in half, too, from what she had been making at 40 hours a week, and she gets that amount even if she works only 18 or 22 hours. As long as you pay her on a salaried basis (appropriate to the number of hours she expects to work regularly) and pay that exact amount regardless of how many hours she actually works, you're fine.