Is opening some body's drawer (locked or unlocked) in the office, can be so rude?Is it unacceptable?

I have my own desk with a drawer in my tiny space in the office room, and it always locked ( even when I go to rest room) most of the time I just sitting there doing things.At the time while I was go to rest room, I have a guess by appointment waited for me in the lobby. I just left my keys hung in the drawer, but still it's LOCKED. I supposed to gave him an envelope of my boss but when I just went out of the rest room, a woman (she is a coworker) had gave the envelope to this guess, I was so surprising. I went numb.Coz I was sure the envelope was inside the locked drawer and this woman was open my drawer without my permition.I just can't accept this. When I asked about this, she only reply "Nothing missing inside there, right?"She is many times always doing other people job. I thought, it's not about lack of job, it is because she is always courious to know somebody else's bussines. How can I react to her after this.How can I avoid her without my boss realize it?She's a good actress

If one of my employees got into another employees desk, I would at the very least give them a write up, if not terminate their employment, for invasion of privacy. You need to talk to your boss about this, because if you don't, this type of behavior will continue and it could possibly escalate into personal belongings be taken. Employees should expect some privacy at their assigned desks. It's good you didn't "react" that wouldn't be a good thing. Think before doing. ;) Avoidance will get you know where, just handle it professional and calmly.

It is office property. If you didn't want her in it, leave out the keys, but unless it is her purse, she is within her bounds.

Yeah she shouldn't have done this. However as it was in connection with the job, and not keeping clients waiting, I am not sure where you would stand, as she said she didn't take anything that she shouldn't.

See if any other colleagues feel the same way you do, i.e is she invading their privacy too? If so, maybe you can bunch together and take it further?

Always lock your desk drawer when you need to go elsewhere. I was robbed once, never again (purse was in the drawer). No one could figure out who did it.

No she has no business going into your desk tell her to keep out.

Depends on what is common practice in your office. If everything is regarded as common property then you shouldnt make a big deal of it. Remember one thing. There is really no sacred private place in an office and no such thing as my drawer, my desk etc. Nothing is really yours. I learned this the hard way. Instead of keeping cash at home I locked it in one of my room cupboards. Always had the key with me. Imagine my surprise when in my absence the cupboard was opened for spraying (against roaches etc) by the custodial staff. Lucky the cash was under a pile of papers and still there. I never thought anybody had a second key. Now I麓ve learned. Nothing in an office is yours exclusively.

Well, ordinarily, no, but she was getting something that had to be got right then for the boss, well, not so bad.
Keep it locked, don't leave your keys in it. A co-worker left a drawer open, with her purse in it, and came back, purse gone. she was only gone a minute, so somebody had seen her put her purse in, and knew where to look.
Put all work items, correspondence, even lock up pens and pencils when you must leave your desk. Make sure your work is off the computor screen. If there is no temptation for her to look, or borrow, it will end.
And you can confront, say things like, Gee, I was only gone to the bathroom a minute, and I come back, and you've been in my space, and took my favorite pen. Wish you could have waited a minute, and asked me. I have several pens I would have loaned you.
And remember, if the office has bought the office supplies, they are not yours, they are community property. And remember, those locked drawers belong to the company, and somebody has an extra key, even a master desk drawer key, maybe even her!

thats invading someone privacy and would royally tick me off

thats not right and you really should talk to HR about her b/c your desk is YOUR personal space and seeing that you did not give her permission to go into a locked space on YOUR desk is an invation of your personal space