storing urine and vomit in bedroom

I'm not sure if I am posting this in the correct forum but hopefully someone will be able to help me.
My 22 year old sister has been urinating in cups and containers and storing it in her bedroom. This has been happening for years. She also stores vomit in her room and it is only removed when when of us family members cleans the room because the smell has become unbearable.
She used to wet the bed as a child and was bullied at school. She now has a good job (in healthcare!!!) and is outwardly happy but there have been problems in the family.
I have spoken to her about this and she claims she does not know why she does this but doesnt want to go to the doctor. Sometimes she says she does it because she is lazy, or doesnt want to go downstairs to the toilet in case someone shouts at her for making noise but at other times she uses different reasons so I feel like they are excuses and dont know the real reason why she wees in her room. And if its just laziness or fear of getting shouted at, why does she keep the urine in her room for months and months?
I am so sure this is a sign of a deeper problem. She has also cut her arms in the past. Its really hard to speak to her about this because she gets angry and changes the subject.
Please can anyone give me any advice?

[crystalfresh]

Sounds like she has a reason if she is getting angry about the subject. Usually I find that people get angry to avoid talking about the true reason and that emotion of anger is to intimidate the person asking to back down and stop asking questions. There is not much you can guess at if they won't tell you. And in lots of cases if you push to know the person will lie about it to avoid telling the real reason. This is not an answer but might explain the anger reason.

Lazy maybe. There are people that will pee in bottles over night or driving on long trips.. But NEVER heard of anyone keeping it. Keeping vomit is something I never heard of unless she thought she was poisoned and is looking to keep evidence. But keeping these things past morning is really kinda strange.... I can't see any motive personally. But since she is getting angry about it I would believe she has a reason.

It does show a serious concern as this could indicate a strong disorder. Unless she has some kind of medical condition where doctors would require her to give samples on a regular basis this would have me wondering... Some kind of phobia maybe.

The next question you might want to know is not how long has she been doing this BUT how long she has been storing the containers. 1 day, 2 days, 1 week... If she is keeping them short term and replacing them could indicate a phobia and she is keeping them just in case. But if she stores them long term weeks, months. Yea I can't even guess at it.

Also it is not normal to vomit. So if she thinks she is sick all the time and going to die or something she might think keeping samples when she feels sick could help in an emergency situation. But this is the only thing I can guess at logically. There might also be no logic to it. Good luck. Either way it sounds somewhat disturbing and hope she can open up to someone.