L.R.
Babies this young don't have "rage" because they are not capable of that emotion. They do indeed have frustration if they are hurting, sick, overstimulated, hungry, uncomfortable etc., but it troubles me that you are labeling it "rage" as if she is intentionally angry. She's not intentional about anything yet; her brain is just not developed enough; she lives in that second of time. It is normal for a child so young not to care about toys; normal for a child that young to want to see a human face (this is the start of learning what other people are). She is not "trying to hurt" anyone, ever; she is simply physically reacting to something in that moment--being in pain, being uncomfortable in whatever position she is in, etc.
If you consider this "rage" and think she ought to be happy with toys -- please get some good books on infant development and find out much more about what she really is going through. She is developmentally not capable of either entertaining herself (and therefore being quiet and happily alone) or being ragingly angry enough to hurt others on purpose.
She also is in trouble. She is in some kind of pain or discomfort and you are interpreting it as anger. Please insist that she get a more complete exam and tests from a doctor -- right now. You say she "just exited a colicky stage" but why do you say that when it seems obvious she's in pain? She may still be IN that stage, or has other issues. The fact she wants, then rejects, a bottle, sounds typical of a child who has horrible gas or colic or other issues -- the baby wants the bottle because she's hungry but rejects it quickly because drinking causes pain, possibly. (Have you never seen this before in a gassy baby?)
This may even be neurological--she may be a child who is very sensitive to stimuli and who is overstimulated a lot of the time and therefore cries and screams.
You and the mom don't need advice on how to "deall with these rage issues" because they're not the real issues. You have to find the underlying problem that is causing this poor baby so much pain or overstimulation. You say her last checkup showed she was healthy but that just doesn't matter -- something is wrong. Her mom needs to see the pediatrician again and demand referrals for some testing to find out what is going on here.
And as others note, never, never try "cry it out" with a young infant. Remember this: If you are not in her presence she believes you are gone, forever, and has NO concept that you are in the next room or that you will come "later." That means absolutely nothing to her at her age! Letting her cry it out means she is lying there feeling utterly alone; that creates a child who is very insecure and only cries more, not less. Please explain this to her mom so you both can work on being with this child and giving her what she needs -- your presence and a real diagnosis of what is going on.