I would put her cup on the counter
I did this
With food, I'd give him just a bite at a time,
and this although usually 2 or 3 pieces but reduced it if there was dropping and throwing.
I would 'catch' DS's arm as soon as I saw he was about to throw or drop something and just take it off him, I'd usually say something positive like 'oh you've finished drinking let me take that for you' and put it on the counter or table out of reach until he gave a cue that he wanted another drink. During 'bad' phases I'd almost keep hold of the cup as I passed it back to him and watched really carefully to see if he was asking for it to drink from or to drop again. If it was for throwing I'd keep hold and just remove it again.
If you can catch the arm/hand just before a throw I am sure it reduces the throwing and helps to keep the meal time positive. When stuff did make it to the floor I totally ignored it (most times - these days he so rarely throws that I now tell him we don't throw food it is for eating or for clearing away) even if it was his drink, he wasn't going to die of thirst within one minute so I just left it on the floor with no reaction and would pick it up after some time had passed to separate the cause and effect aspect of the game (I drop mummy picks up, great, I drop again, mummy picks up again).
And, at the end of every meal I offer a plate, bowl or my hands to 'clear up please'. This is, in effect, a filling and dumping game but you guide where the dumping goes (on the plate) and give lots of positive reinforcement for each item being picked up and dumped on the plate and thank LO for such lovely table manners when they have finished clearing up. The trick with this is to totally remove the plate once all the items have been dumped on it (mine also dumps his fork, spoon and cup) to prevent the next part of the game which is emptying the whole thing out again.
I have not found a problem with a particular age (DS now 16 months and been clearing up since we started solids at 6 months) but I have noticed that there are long periods of lovely clearing up and zero throwing then suddenly he'll drop food over the side again. It's always at the same time or just after some other developmental milestone as though he knows the rules of the world have changed (from crawling to cruising perhaps) and things that weren't possible before are now possible and he tests all the 'old' rules to see if they still apply. After one or two meals with some dropping and my intervention we get back to clean eating again (it's really important to intervene quickly at these testing points I think). Because DS is generally so good at being clean at the table and has already established the 'rules' I have moved on to telling him 'no, we don't throw food. Food is for eating or clearing up' and I pick it up, hand the item to him and immediately say 'clear up please' and indicate the plate.
One other particularly noticeable time is if DS needs to pee or poo. He will suddenly throw food. If I give him a chance to go potty or go in his nappy and a nappy change he will then eat nicely again.
