Mabufu is of questionable use in Persona 4 Golden against Shadow Yukiko. In the original version of Persona 4 it was useful for Chie to cast it once to get an extra turn off the prince (then using a single target to not damage the prince any further), but in Persona 4 Golden the prince's weakness was changed to Electricity. And while Shadow Yukiko has a weakness to ice, she will very likely have White Wall up most of the fight to make exploiting this pretty difficult. That being said, the Prince is more dangerous in Golden due to having a higher magic stat (more potent heals) and Makajam, so it's generally a good idea to keep it in dizzy status with electricity attacks if you can.
The persona Senri is exceptional for this fight in both versions of the game. It has a resistance to fire nullifying some of Shadow Yukiko's strongest attacks. It comes with the healing skill Dia out of the gate, and when leveled up a few more levels it earns Media making your protagonist the ideal healer for this fight. It can also inherit Red Wall, Resist Physical, and Tarunda from the persona Slime too, allowing the protagonist near perfect immunity AND giving him some decent supporting options alongside that healing.
Remember tho, Visualante. Persona 3 and 4 are generally not games where you need to grind. Most of the time, simply switching your strategy around and bringing out new Personas can make all the difference in the world. You can definitely still finish the dungeon with one day left thanks to the new SP restoring mechanics from Shuffle Time and the help feature. It's also possible to farm SP restoring items on the lower floors, although it's tedious. And as noted, you can simply let time pass and travel back a week in order to get a fresher start.