Well, Im not like all those dude askin for an interrupt or a reduce of mana cost (which would be good anyway).
Simply, change the skill line, which at lv 15 gives +4 gold, into a line of 3 skills (lv 5, lv 10, lv 15).
In those, each of the point will give an additionnal small boost to summons and give +2 gold.
At lv 15, it would give a big boost to summons and +6 gold.
Queen will then be a pure support.
She will shield allies, AoE, and can be used as the main citadel upgrader in maps like Leviathan and Prison where Gold is scarce.