If you use a 125, you should be prepared to use an egg crate divider with an opening small enough for the female to get away from the male, and of course too small for the male to get thru. I agree with RD bigger would be safer, but there are no guarantees even a 180 or 200+ would protect her, without a divider.

The tank above is 6ft, and I kept the divider in permanently.
Another option would be to use target cichlids that distract the hormonal urges into the protection mode (but then again, there would be no guarantee they could actually be enough of a distraction).
I sometimes could put target fish behind a divider, and it occasionally worked.
In most of my cichlid tanks (whatever species) dividers were the norm.

I even kept a permanently divided bucket for picking up, and transporting pairs.

a divided beanii tank below
