The 23-year-old beat Boaz Myhill from 25 yards to cap an impressive comeback by the visitors after the superb Shane Long had given the home side a commanding lead.
Shane Long gave the home side a commanding lead inside 11 minutes with two superb goals, first plucking a Chris Brunt pass out of the air before firing home and then smashing the ball over Brad Guzan.
But Karim El Ahmadi pulled one back for the visitors midway through the second half, before Westwood levelled matters with his first goal for the club.
|VIEW FROM THE HAWTHORNS
|By Chris Davie
"Shane Long’s superbly taken double inside the opening 11 minutes provided the perfect start for Steve Clarke’s side, who dominated the first half and capitalized on Aston Villa’s lack of width.
"However, credit must go to Paul Lambert for his trio of changes in the 57th minute which gave time for the visitors to mount a revival, as well as offering options out wide which were lacking before the break.
"Karim El Ahmadi took his effort well from close range but Ashley Westwood ensured Goran Popov’s woeful clearance was punished to the fullest extent with a fine strike from well outside the box.
"Both sides have secured just one win in their last six Premier League matches but are five points clear of the relegation places."
The hosts started fast and went ahead through a piece of individual brilliance from Long in the third minute. The Republic of Ireland international wonderfully killed a Brunt pass with his first touch, took the ball around Nathan Baker with his second and then side-footed beyond Guzan for his second goal in as many matches.
Paul Lambert’s men almost hit back instantly as Aleksandar Tonev’s powerful long-range strike was saved by Boaz Myhill, who got down well to his right.
Long then got his second, capitalizing on a misplaced Leandro Bacuna pass to take the ball beyond Baker once again and clip a sublime finish over the helpless Guzan and into the back of the net off the underside of the crossbar.
Stephane Sessegnon could and should have made it three eight minutes later but diverted wide of the left post from a Morgan Amalfitano cross when it appeared easier to score.
Libor Kozak clipped the crossbar at the other end in the 25th minute, receiving the ball from a Christian Benteke header before pulling off a sweet strike on the half-volley.
Long was in inspired form and charged through the Villa defense on the half-hour mark before firing his eventual effort straight at Guzan from 18 yards.
Sessegnon missed a second glaring opportunity in the 64th minute, blazing over the crossbar from eight yards out.
It was turning out to be a night to forget for the Benin international and Villa got themselves right back into the tie three minutes later when El Ahmadi got his boot on the end of a Andreas Weimann header to lift the ball over Myhill.
And Westwood completed the Villa fightback 14 minutes from time, receiving the ball from a loose defensive header and firing a thunderbolt into the bottom right-hand corner.