I can't remember what exactly I did on my first playthrough.
I tend to grind pretty heavily, so my units were all very high level at that point.
I buffed out someone (possibly Alicia) with the set of defensive orders that would buy time between Selvaria's fire, which has a slight lag time.
I might have used smoke one one of the long stretches, but the goal was to get a foothold on one camp out of her line of sight.
After that, a shock trooper or was enough to hold the flag against limited enemy attempts to take it back, and I could summon up troops to move to the next flag.
Selvaria would helpfully yield ground, for some reason.
There's also a slight cheap factor I used in one take-down, where Selvaria had moved to the left rearmost part of the map, and I had a set of troopers behind some sandbags and a scout on a lower tier in front.
I was able to take potshots with a scout from the lower level where a few bullets would just barely go over a railing and hit her in the head.
Her shots, like all AI shots and return fire shots, aimed lower and hit the railing.
I could then spray with trooper from the sandbags, rinse and repeat.
I tend to grind pretty heavily, so my units were all very high level at that point.
I buffed out someone (possibly Alicia) with the set of defensive orders that would buy time between Selvaria's fire, which has a slight lag time.
I might have used smoke one one of the long stretches, but the goal was to get a foothold on one camp out of her line of sight.
After that, a shock trooper or was enough to hold the flag against limited enemy attempts to take it back, and I could summon up troops to move to the next flag.
Selvaria would helpfully yield ground, for some reason.
There's also a slight cheap factor I used in one take-down, where Selvaria had moved to the left rearmost part of the map, and I had a set of troopers behind some sandbags and a scout on a lower tier in front.
I was able to take potshots with a scout from the lower level where a few bullets would just barely go over a railing and hit her in the head.
Her shots, like all AI shots and return fire shots, aimed lower and hit the railing.
I could then spray with trooper from the sandbags, rinse and repeat.