Whenever you're up against a Maeve, your Fireball will be necessary as Maeve is more than able to kill you from a distance. If you're alone with a Maeve and not at low health, you can put up your shield and retreat, or burn her with the fireballs.
Maeve will always use her speed against you. She will also use the high ground and distance. Close in on her and try to lead her into tight, walled environments, where it is easier for you to just flame and fireball and charge.