I'm reading that Gwendilyn is entitled to 36,000 gp in magical items.
I will give her these items now, in an effort to compliment the character.
(looks uneasy, since this kind of thing was uncommon in 2nd edition)
+3 mithral breastplate
+2 keen rapier
+2 ring of protection
Only 3 weapons in the game benefit from both Power Attack and from Weapon Finesse: the rapier, the spiked chain, and the whip.
The spiked chain and the whip both require 2 hands to use.
This means the rapier is the sole instance of a weapon where two such weapons could be used, and benefit from both Power Attack and Weapon Finesse. Or so it seems.
Since it would require a feat to allow for competent two weapon fighting, because nobody historically fenced with two rapiers, and because bladesingers prefer to fight one-handed (they can't use bladesong any other way) I will assume that ... Gwendilyn is not using her off-hand at all.
I'll give her a short sword and a dagger, the weapons of history to compliment her primary hand, but it's doubtful she ever uses them.
This will, of course, reduce Gwendilyn's damage capacity. With a +2 keen rapier, she threatens on a 15-20. A successful critical causes double damage, as usual.
Her attack bonus rises to +14/+8 with this weapon.
Her damage on successful hits would be:
1d6 +1 weapon focus +1 str +6 int +2 enhancement: for an average of 13.5 points.
If she struck and hit twice, damage would rise to 26 points (half str bonus)
If she used all her BAB in power attack, her damage would rise to 40 points (but she would only do that, as a friend of mine noted, for opponents with AC 10 or under special circumstances.)
If she used Haste and thus attacked thrice, without power attack, damage would be 40.
If she used Haste, attacked thrice, and used full power attack, damage would be 61.
If she was fortified with bear's strength and fox's cunning (a pity they nerfed those spells ...) then her damage would further increase to 73.
If Gwendilyn used haste, her whole power attack, arcane strike, bear's strength and fox's cunning, and hit with all attacks, her average damage would be 73 points.
(chuckles) A much nerfed version of my 180 point devastation assault, no?

But hey, I'll take 73 points of damage in a single round any day, and I'll bet most others would too.