Reach across cover and bodyguard

[Cuttler]

Can Bodyguard be used to help ally if opponent has cover, but you can reach him (because of enlarge or reach weapon)?

For example, imagine a situation where a big troll (large creature with reach) is in melee with two side by side barbarians and an enlarged fighter with the bodyguard feat, like depicted below:

TT
TT
BB
FF
FF

T: the 4 spaces occupied by the Troll
B: the 2 spaces occupied by the two barbarians (normal medium size)
F: the 4 spaces occupied by the enlarged fighter

[Magda Luckbender]

Bodyguard Feat wrote:

Benefit: When an adjacent ally is attacked, you may use an attack of opportunity to attempt the aid another action to improve your ally’s AC. You may not use the aid another action to improve your ally’s attack roll with this attack.

Yes. Bodyguard does NOT say that you must threaten the attacker, although a few people interpret it this way. There has been considerable discussion on that very topic.

The way you drew the situation, Bodyguard would apply with BOTH interpretations. Soft cover has nothing to do with anything in this case, as you are NOT taking an AoO against the attacker.