Defender Cooper, who joined the Magpies from Reading Women in the summer, popped up at the back post to meet Freya Gregory's free kick and slotted home like an accomplished striker.
Newcastle's number 12 was pivotal at the weekend as the Lasses were pegged back twice by Bristol City Women at Kingston Park, with Cooper insisting that she never doubted the three points were staying on Tyneside.
"We played some good football and certainly controlled the first half," she said. "I'm just so proud of the girls and it's a great start to an important month.
"As soon as they equalised for the second time, I just thought we would go and get another goal.
"I remember waking up before the match and thinking we're winning today, and then at no point during the game did I think we were either going to draw or lose the match."
The former Chelsea Women defender has enjoyed her time at Newcastle in both boxes, with United boasting the fifth-best defence in the division, alongside her three strikes in black and white.
Two of those goals have come in the Women's Championship, with her first being a last-gasp equaliser at the back post against Southampton Women at St. James' Park in November.
But there was a heart-in-mouth moment for the dominant centre back just as the ball hit the net on Sunday.
"I actually thought I was offside," Cooper admitted. "I didn't realise it was a Bristol City player who flicked it on, so when I looked over and saw the goal had been given, I was relieved.
"It's my second goal at the back post this season, and I'm just loving going up for free kicks and corners."
Despite a recent two-week break, Newcastle now have another week off due to the Adobe Women's FA Cup, but Cooper sees it as an opportunity for some good preparation on the training pitch.
"We knew it was important to get off on the right foot this month because we've got some huge games, including two local derbies," she added.
"It has been a little bit stop-start this season, but ultimately it gives us two weeks to prepare for a big game against Durham, and that's always better than a quick turnaround."
Newcastle United Women's next home game is against Sunderland Women at St. James' Park on Sunday, 23rd March.
The Magpies are set to break the Women's Championship attendance record - and are hoping to break their own record of 28,565 for a women's game - by packing out St. James' for the derby clash.
Tickets are currently on general sale here at an advanced online price of £8 for adults and £2 children, with a £1 donation from every ticket sold going to Newcastle United Foundation. Hospitality and premium packages are also available.
