Grappling strike fighter power with brawler style – attack roll bonus

I (the DM) have a player with a level 11 fighter (brawler style). She uses the power "Grappling strike" (Martial Power 2 p7) with a bastard sword (+2), and we disagree on bonuses to attack roll.

The power states:

Hit: 1 [W] + Strength modifier damage, and you grab the target. The grab ends automatically at the end of your next turn.

And the brawler style (Martial Power 2 p6 with errata) states:

In addition, you gain a +2 enhancement bonus to the attack rolls of unarmed attacks and a +2 bonus to the attack rolls of grab attacks and attacks to move a creature you’re grabbing. These bonuses increase to +4 at 11th level and +6 at 21st level

She thinks the attack roll should have the brawler style bonus (+4 at level 11). But I think that bonus should not be counted, as it is for grab attack only, and grappling strike is an attack with just a grab effect/consequence.

I think the brawler style applies only to the grab action, describe in PHB 1, p290.

As English is not our native language, we may misunderstood this bonus.

A +4 bonus at level 11 seems a little overpowered for an at-will power, it can change:

1d20 + 17 (5 half level, 5 str, 3 proficiency, 2 alteration, 2 feat)

to:

1d20 + 21

A standard monster has 25 AC (DMG 1, p184): she will hit on 4+!

Can you please tell us which understanding is right ?