Everton stood firm against Jonas Eidevall’s side for half an hour, but the hosts gifted the Gunners four goals in the quarter of an hour before the break, as Caitlin Foord struck twice, while Katie McCabe and Lotte Wubben-Moy also got in on the act.
But the Gunners’ victory, which aided their Champions League qualification hopes, was marred by a horror injury to Lia Walti, who was stretchered off after Aggie Beever-Jones caught her high on the ankle.
Beever-Jones was eventually sent off for the challenge, after initially being only booked, but Arsenal failed to make the most of their player advantage. In fact, their goal difference took a hit as Katja Snoeijs found the top corner from a free-kick for a late Everton consolation.
But, just before the half-hour mark, the deadlock was broken. Blackstenius forced a mistake from Everton as they went short at a deep throw-in and the ball broke to Walti.
The returning Arsenal midfielder fed Foord in the box and she swept past Emily Ramsey with an effort off the post.
Everton nearly equalised straight from kick-off as Wubben-Moy gave away the ball cheaply to Snoeijs, who had a one-on-one. The England centre-back managed to get back in time, though, to deny the Everton striker with a superb last-ditch challenge.
Moments later, Arsenal doubled their advantage as McCabe struck from 30 yards, beating Ramsey in the bottom corner after Everton gave away possession cheaply in their own half again.
Everton goalkeeper Ramsey then made two routine saves from Foord and Blackstenius, but the hosts failed to recognise the warning signs.
For Arsenal’s third, Frida Maanum fed McCabe down the left and her cross was met by Blackstenius, who forced Ramsey into a good save. The rebound fell to Foord, who headed home with five minutes remaining until half-time.
Everton needed just three minutes to concede again as Blackstenius won a free-kick on the byline, leaving Maanum to cross for Wubben-Moy, who headed home while unmarked.
In a quest for more goals, Eidevall made an attacking half-time change as Jodie Taylor came on for defender Rafaelle Souza. But it was not long before Arsenal were forced into another change in unfortunate circumstances.
Beever-Jones took a heavy touch in the box and caught Walti on the ankle, much to the fury of the midfielder’s team-mates.
The referee initially punished Beever-Jones with a booking but, after consulting her assistant on the touchline, upgraded it to a straight sending off. Walti, meanwhile, was taken off on a stretcher in a blow for Arsenal and Switzerland’s World Cup squad.
Arsenal looked shell-shocked and failed to take full advantage of their player advantage. Taylor headed over from close-range after McCabe’s cross found her a few yards out from goal, while Gio Queiroz struck the post late on.
Ramsey also had to be equal to low efforts from Taylor and fellow substitute Katharine Kuhl.
In a laborious half for Everton, they eventually had something to shout about with 10 minutes to go when Snoeijs headed a corner high into the net, with Arsenal showing a moment of hesitation.