The victory also made sweet amends for last season's 61-36 setback to Xavier in a contest played in Cincinnati. Xavier had won three straight meetings in the series.
"It feels really great to get this win," said Johnson, a senior guard. "I've been here for four years, and we've never beaten Xavier. It was nice to get a little taste of revenge."
While the Musketeers (1-1) are in the atypical position of not being nationally ranked, the Xavier squad is still five-time defending champions of the Atlantic 10 Conference.
"I realize that Xavier lost some players, but four of those players (played) against us last year," MSU head coach Sharon Fanning-Otis said. "They had some players that had been really successful together, and a couple of transfers which means they were another year older (and came) from some pretty good programs."
Alwal, the reigning Southeastern Conference Freshman of the Week, scored 14 points and pulled down a team-high 11 rebounds in 32 minutes of work. This effort came on the heels of 11 rebounds and 10 blocked shots in MSU's season-opening win over Jacksonville State.
Xavier started strong Monday night, sprinting to a 10-2 advantage at the first media time out. Johnson scored on two of her team's next three possessions to bring the hosts within 10-8. Xavier ran the lead back out to 16-9 and still led 18-15 before defensive pressure started the game-deciding run.
A jumper by Alwal placed the Maroon and White in the lead for good. Porsha Porter followed with a steal and fast-break layup. Another Xavier turnover led to Ashley Brown layup as the hosts grabbed a 25-18 lead with 7:43 left before halftime.
The Lady Bulldogs eased into halftime with a 37-32 advantage. Despite allowing 53.8 percent shooting from the field, the Lady Bulldogs offset that by forcing 12 first-half turnovers. Xavier also had a 21-15 rebounding advantage at the break.
In the second half, the Lady Bulldogs took matters on the defensive end and seized complete control of the contest.
"We changed defenses on them, but we gave up some layups because we did not have the weak side help," Fanning-Otis said. "You saw them with a couple of open threes. But, hopefully, we will get tougher and learn from each other.
"When we had a 13-point lead, I had hoped that at that point we could put a team away. That's something we have to grow into."
After Xavier closed within 37-35, the Lady Bulldogs moved back out to a comfortable lead with a 12-1 run. A layup by Porter gave the hosts a game-best 49-36 lead with 14:37 remaining.
Xavier did hang tough, reeling off eight straight points to close within five. The Musketeers would get within two on three different occasions in the second half, including at 67-65 with 53 seconds left. Johnson, who finished with eight second-half points, sank four free throws to close out the victory.
"During the second half, I was really trying to get everyone involved, but things weren't really falling for them," Johnson said. "I knew it was time for me to take over. I was comfortable with myself taking those shots."
For the contest, the Lady Bulldogs hit 28 of 69 shots from the field (40.6 percent), 3 of 9 shots from 3-point range (33.3 percent) and 12 of 18 shots from the foul line (66.7 percent). The Musketeers hit 22 of 51 shots from the field (43.1 percent), 7 of 22 shots from 3-point range (31.8 percent) and 14 of 20 shots from the foul line (70.0 percent).
Xavier held a 43-37 rebounding advantage. The Lady Bulldogs had 13 assists and eight turnovers, while the Musketeers had 15 assists and 19 turnovers.
Porter was also in double figures with 14 points, while Brown pulled down seven rebounds in 21 minutes before fouling out late in the contest. MSU had a remarkable 13 steals, including six by Porter. Johnson dished out a team-high seven assists.
Xavier received a double-double from Jessica Pachko (14 points, 11 rebounds). Others in double figures included Tyeasha Moss with 14 points, Shatyra Hawkes with 12 points and Lynette Holmes with 12 points.
MSU concludes its season-opening three-game homestand with a 7 p.m. start against Alcorn State Thursday night.