On paper it's recommend one adult GT is kept in a 55-75g depending on who you ask. It's more about the tank width than height, so they have lots of swimming space. A long 75g is better than a tall one. With good hiding places you will get away with both in there long term even if she stays smaller.
They don't tend to grow too quickly in my experience. If she doesn't grow as quickly as him you may have problems if he is a meanie. If he turns into a bully when they are bigger you may have to put in a lot of hiding places that the female can get into, but the male cant.
Cheap terracotta pots are perfect for helping with aggression in pairs, and they come in so many different sizes that you are bound to find the perfect one that allows her in, but not him. Alternatively, drain pipe is also good and comes in a few sizes. Both are cheap too!
Remember to feed her extra while she is spawning to help prevent her growth being stunted.
A small group of non cichlid dither fish would help to calm the male down, silver dollars are good for this and they get big enough that they won't be eaten by them, but long term, they would get too big to use as dithers in that tank. If they bother the eggs when they are laid, just move them to another tank temporarily. Be prepared to potentially lose the dithers during spawning, they can get very aggressive, but it will help take some of it away from the female.
Don't forget to pop in some slate or smooth rocks so that the eggs can be moved out once fertilised if the pair start to eat them - that does happen occasionally. Another bonus point for terracotta pots is that I have had many a fish lay on the top of them, and they are easy to remove. I think the females like them because they feel safe in the pots because the male can't get to them, so they think it's a good place to spawn. You don't want them to lay on the floor or the wall, because then you can't remove the eggs. Offer them lots of surfaces to spawn on, they will pick wherever they feel most comfortable.
Also, another quick tip, if you notice any white furry stuff growing on the eggs once they are laid, put in a very weak solution of methylene blue and put a small airstone next to the eggs to aid circulation - it will help to prevent the fungus from spreading.
I have had some pairs where the male was a gentle giant, and some where the male abused the female and was a psycho.