United ran riot at Kingston Park, beating Huddersfield Town Women 10-0 in front of a record 7,382 attendance, and Lumsden helped herself to a brace with goals in either half which made that victory taste just a bit sweeter.
Newcastle went into their game against the Terriers knowing a win would see them secure the league title and promotion into the FA Women's Championship, and when Emma Kelly opened the scoring after just 11.6 seconds to ignite the party atmosphere, they were already on their way.
Since joining from Portsmouth in January Lumsden has made a big impact on Tyneside with three goals in nine appearances, and fans have warmed to their winger straight away.
"I'm just lost for words right now," Lumsden told nufc.co.uk moments after lifting the trophy.
"This is an amazing football club and an amazing group of players. It was just such a top performance from everyone who started and came off the bench given the circumstances.
"This feels so good. We're ready for the Championship and so excited to be where we think we deserve to be."
A record-breaking crowd for any sporting fixture at Kingston Park this season showed their support for the Magpies - who only lost once at home all campaign - and enjoyed seeing the club's biggest league win all year.
Newcastle have been one of the best-supported teams all season, both home and away, but there were two special fans in the crowd cheering Lumsden on for one final home clash.
"Before the game, my parents were hoping that I'd get a goal so I'm really happy to have done it for them and top off a great day all around," she added.
"I've been at so many football clubs and nothing comes close to these fans. They're just unbelievable, I can't really put it into words."