She's always been good. Its just later on writers forgot and focused more on her mind abilities. She was trained in the alien martial arts of Titan by the monks there IIRC.
Even when she fought Cap(Cap was hindered at the time) she stated she always wanted to test her alien art vs Cap's honed experience. In that contest she won.(but could she have defeated Cap without the SSS degenerating...will never know unless the rematch)
Another time Daredevil a very known pressure point fighter would out skilled as Moondragon used her alien pressure points to give him back his sight.
And to top is off she even floor a energy being that gave Thor trouble, to later of course proving that she was better then Mantis in hand to hand combat.
So her martial art background was always there just later on ignored.
Gender: Male Location: Planning to take over the WORLD!
what's so hard to believe? she wasn't even sure she could beat strange....
in all seriousness, i've never really gotten all the mantis hype. someone feel free to show some scans of something impressive and i'll happily change my mind....