OOC: In the words of the 3.5 MM, "Golems have immunity to most magical and supernatural effects, except where otherwise noted." Quoting the MM 3.5 again: "Flesh Golem ... Special Qualities: ... Immunity to Magic ..." BONUS INFO: Flesh Golems have Damage Reduction 5/Adamantine!!!!!
OOC: Still looking at this, Bro. The Golem's Immunity does specify immune to any SLA that allow spell resistance. Which book contains Francheska's Fiery Burst ability?
OOC: Sorry for the slow reply, just back from Dallas.
Instead of the SRD, try the PRD on flesh golums, which is very clear:
"Immunity to Magic (Ex) A flesh golem is immune to any spell or spell-like ability that allows spell resistance. In addition, certain spells and effects function differently against the creature, as noted below."
As I said before, as the DM, especially of a Pathfinder game with 3.5 elements retained, if you rule that the flash golum is immune to the Fiery Burst, that's fine. As written for a pure Pathfinder game (where Fiery Burst does not exist), the flesh golum would not be immune.