No i dont think SSkrull could put out heat at a level of Firelord, maybe equal or comes close to it w/ outside sources.. Unfortunatedly for him he doesnt have that advantage against a physical opponent but WW still in need of oxygen to breath and is present in her system which SSkrull can take advantage of by setting it a fire.. She will not only have no O2 present in her body, her inside would be a flame and dehydrated.. That kind of damage inside her would probably take her out..