Is it appropriate for me to...?

Would it be appropriate for me, (30 yrs old), single mother of 2-year-old boy, to go to work, speak to everybody in the room, and then not say-so anything for the rest of the day to anybody, unless asked, or told by higher authority to do something? Is this considered rude? I'm asking because a co-worker of mine, (mid 40-ish), single parent of teen son, whom I thought we were fully clad acquaintences, threw a set of master security keys at me on Sat, and grabbed the correct set. She have an attitude all day, didn't speak to me, then when the subsequent shift came on to relieve us, she spoke to them and talked with them usually, after she had been a butt all time to me. I did nothing to her, don't talk to her outside of work or anything, we were chitchat and laughing just fine Friday, and then Saturday, she was surrounded by her moods, and threw her keys not neccessarily at me, but I was facing the direction in which the key were thrown. So am I wrong today to say hi, and then mind my own business, and not speak anymore to her, since she can give somebody a lift her moods out on me, when she feels like it?
She is 40 something hormones going delirious about now so take it unproblematic on her every women alive has them some worst than others so try and be nice until you figure out if it's that or is she mad roughly speaking something maybe you should ask her could say did i do some thing to upset you
Rude? I call it abusive. Talk to your boss. It's not your problem if this woman go psycho on hormones, as "Angel" suggests. If your co-worker brings a gun to work one day and shoots everybody dead, should she be exonerated because she was basically having a "bad hormone day"?

ETA: For the record, hormones now and then cause that kind of behavior. I think the woman is clinically insane.
Answers:    At 40 it's not necessarily her hormones I'm fifty one and have not reach that stage in life yet.So she may a short time ago be a moody person trust me I have worked with plenty who be.I do agree you should see how things go before just keeping to yourself but if she is going to be rude sometime and then nice the next repeatedly then I would simply speak to her when spoken to.But it is still a wait and see situation.
I would ask her surrounded by a quiet moment what was going on the day she threw the key. I'd ask if she was upset for some reason, the key throwing seem like a comment, rather than the random expression of anger which she may enjoy unintentionally directed at you. Ask.
Do not apologize, you have not done anything wrong, just ask if she is okay, and if near is anything you can do. She may appreciate your expression of concern for her. Just let her know you noticed she was upset the other light of day, and wondered if she is all right. That's all you can do. The rest is up to her.

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