. . . How hard can it be?
. . . I can't tap my foot at a consistent pace, and just like counting out loud, it is a distraction and ruins my ability to play.
. . .
Do you mean:
. . . "I can play at a consistent tempo if I don't tap my foot"
. . . "I can't play at a consistent tempo, and tapping my foot doesn't help" ?
FWIW (I don't teach) --
As several people have said, it's difficult to play with a metronome that's ticking at less than around 60 bpm -- the interval between ticks is too long. So avoid doing that.
What I suggest, as a way of getting used to "playing , guided by the metronome":
Set the metronome at a speed around 120 bpm. Right hand only, play a scale (one that you know, not a new one!) with one note per tick. Practice that until you can do it -- no rushing ahead, no falling behind.
Do the same for the LH. Then do it for both hands together.
(You may think this is too easy for you -- it's probably about right.)
Now, set the metronome to a little faster - say 130 bpm. Do the same exercises, until you can play with the metronome.
Set it to 140 bpm, and repeat the exercise.
Now, set the metronome to 70 bpm. Play the scales at the same speed, but you'll be playing two _evenly spaced notes_ on every tick.
Speed up the metronome gradually, to around 105 bpm. You should be able to handle that (I think) -- two notes per tick -- at Grade 4.
Set the metronome to around 70 bpm (2/3 of 105 bpm). Practice the scales at the same speed as before, but you'll be playing _three_ notes per tick. (you may want to accent the scales in triplets -- talk with your teacher if that causes problems.)
When you can do that, _then_ try playing a piece of music that you know well, at a tempo you can easily handle, with the metronome running _at that tempo_. It will feel strange -- the metronome puts you into a rhythmical straitjacket. But you will -- eventually -- be able to control your rubato (or just involuntary tempo changes) to match the steady tick-tick-tick of the infernal device.
And _then_, you can start to use it to _slowly_ increase the speed of difficult passages.
Stay in touch -- the process isn't easy, but it's worthwhile, IMHO.
PS -- It would be a _really_ good idea to talk this over with your teacher. She may have other ideas, and you're probably better off following her, than following me.