Hey just be glad she is drinking water :) I am almost 28 weeks and have a hard time with it some days. Glad you are concerned though. It means you care a lot and thats very important!!! But she can drink water cold or room temp. I prefer cold water but again its just a preference. A good book you could get is Your Pregnancy Week by Week. Its got tons of information and its an easy reader. Also has dad tips in it which are good :)
I agree with the above posts. The only thing I want to add is don't let her drink bottled water that the sun got a chance to warm up, even if she cools it down. The plastic expands with the heat and release some harmful things.
Really doesn't matter. Only thing she will find is later on when she feels movement drinking something cold will make baby more active.
Water is water whether it's cold or room temperature. So it doesn't matter.