Wanting to make DB squats more intense, might consider the one and one half program.
Do a full squat, than come up half way...stop....and down again to the full squat position and back all the way up to the original standing position. That's a 1 & 1/2 rep. No bouncing from that bottom position, try to make a true BB'ers full squat every rep.
Might suggest(with your DB's) the Bulgarian squat and front Step-up. Both hit the ham's & glutes very well, also. Most trainee's hold a DB in one hand, rather that both. Seems to allow more focus on the one side you are working. Would also suggest the Romanian DL, because the back is held straight throughout the entire movement.As with the SLDL's, people tend to round the back, which allows too much tension on the lower spine.
Might also suggest, if your lady friend is so concerned about your body mass and glutes, she set you up for a membership in a real weight training gym. But than again, what's love got to do with it? Good Luck with that.