Her counterpart of the Indian pantheon, Rama, got possessed by an evil powerful god or something like that, and was going berserk. So a godly champion type, and reasonably close to her power level, plus the power of another god or so. He defeated her pretty quickly based on raw power.
Then, she called on the power of the godwave and went from wounded to beating the *heck* out of him, with her primary worry being to finish the fight before the power overwhelmed her rather than anything he was doing.
This is the only example I know of of her using it, but it seems to be quite a significant power boost if short-lived.
The wave seems to increase her power considerably, but judging from the environmental damage to the city (via shockwaves, etc) it doesn't seem to be substantially higher than we've seen from the likes of Hulk, or Thor at their best. (pre-skyfather thor vaporized mountain ranges with the shockwave from one hit, Hulk was destroying the eastern seaboard with his steps, etc)
Surfer's advantage is, and has always been his versatility. If you can think of an ability, he's probably had it at some point, and in this case the advantage here is his defensive capabilities.
from that scan, diana clearly can't maintain that power level (burning her, going to consume her, per the scans) so if surfer is able to simply avoid her assault until she burns out, the godwave isn't really going to be much of an advantage.
Since we know surfer can render himself intangible, shrink to submicroscopic sizes, and shift between dimensions as needed- I'd say he has a good chance of simply evading diana's godwave boosted attacks until she's forced down to normal levels.
All this is assuming that Diana's power with the godwave is stronger than he can simply absorb or block, of course.