Add to that Erza has her Wind Empress Armour to counter Sherria's winds.What TO Sherria showed against Dimaria: 10 seconds of CQC, then a God Slayer Art. With only that, TO was gone.
If you're thinking that this would be enough to defeat Erza before TO runs out, i'll have to disagree.
Her other spells (you named Sky God's Bellow and Boreas) would also consume her time of TO just like her GS secret art. At the ed of the day, she won't be able to best Erza's durability with such a low TO time.
Cannonically, the maximum TO can accomplish before Sherria runs out of magic forever is defeating Chronos. Immediately after that, TO is gone, which is a fact. Her GS magic being super effective against Dimaria, it is my belief that this power needed to defeat her isn't enough to defeat Erza.
EVEN if we assume her extremely limited ammount of TO time is as destructive as an Irene's claw swipe, Erza would still be able to beat Sherria.
This will give Erza a huge advantage.