The "trait increase did nothing" issue is almost always due to a player not taking into consideration equipment trait bonuses. So double check what equipment you were wearing before and after trait increase.
Keep in mind for Clerics, INT raises mana for every 2 points, thus increase at 2,4,6,8 etc. No half-way bonus for 1,3,5,7 etc. Thus if Hirge has a baseline (natural) INT of 1, AND wearing a +1 INT item (ring, amulet etc), she would have a final INT of 2, given her the mana bonus. Raising her baseline from 1 to 2, would increase her final INT to 3, which does not give a mana bonus to clerics. It does given other INT benefits, including trait check ability.