Fisticuffs Skill Set for Jessica
Jessica's Fisticuffs Skill Set comes with a passive trait that works while she is equipped with any weapon; making it more worthwhile than some of the other characters. Her Thin Air ability, the most useful ability in Fisticuffs for each character is 68 points in instead of the typical 42 which means you do not want to get the ability on her. It'll cost you far too many valuable points.
Assuming that you're playing the game without cheats I wouldn't recommend you putting 52 Points into Fisticuffs for Evasion Up. Jessica, like Angelo, needs to raise 3 Skill Sets to max in order to get all of her abilities. Her primary weapon Skill Set (Whips usually), Sex Appeal and Staff if you plan to get all of her spells. That leaves very few extra skill points for Fisticuffs.
5 Points: +5 Attack while unarmed
13 Points: +10 Agility while unarmed
19 Points: Stone's Throw - Attacks a group of enemies and deals between 5 - 20 base damage.
28 Points: Critical Hit Chance Increased while unarmed
35 Points: +20 Attack while unarmed
45 Points: Harvest Moon - Hits a group of enemies. The attack deals 50% more damage than a regular attack but the damage is divided amongst each enemy hit.
52 Points: Evasion Up - Your chances of dodging an enemies attack is increased. I'm fairly certain this works while unarmed.
68 Points: Thin Air - Attacks all enemies. Deals 40 - 50 base damage and up to a total of 135 damage. Jessica's level affects how much damage this ability does.
85 Points: +35 Attack while unarmed
100 Points: Magic Burst - Uses all of your remaining MP. Hits all enemies. Causes damage based on how much MP is consumed 1MP = 2 damage. This is the single strongest ability Jessica can get but isn't too useful since all you get is one hit.