My suggestion is: Just draft a letter ,kind of "invitation letter" and put your address and stuff so that the visa consular knows where your sister will be staying during her visit. You can add one more sentence that your sister is just visiting and will leave USA per her visa deadline or sooner to ensure she does not stay longer. Other than that, your paystubs, H1 recipt's copy etc would be helpful.

@sajhababa bum bum bhole: Chances are very little that she will get a visa. Need a lot of paperwork done. Have your sister ask letters from her school from as many departments as possible. Letter from your parents and prove that your parents have a tremendous amount of money in the bank. Need to prove a lot of things. To me, it's not even worth it to hassle.

Given the circumstances that she could be in her low 20's and studying, it might be difficult to get granted a visa, but should try will all possible documents n hope for the best.
Following should be required at a minimum:
1. Your letter of invitation and affidavit of support for your sister's travel and temporary stay in US
2. You bank statements, income verification, tax returns, empliyment verification
3. Your proof of legal stay (h1)


4. Your sisters legal status proof in Germany
5. Letter from your sisters college saying she is studying full time and that period in September is College break and that she is enrolled in the semester following the break
6. You and your sister's relationship proof- family relationship certificate probably from Nepal ( how does the consular know u two are siblings??)
7. Who is supporting her financially in Germany? U or ur parents, affidavit of that and proof of source of finance to prove that she will return back to germany to complete her study

Sajhababa: I have seen many students from Europe granted visitor visas to visit the US. I think it definitely is worth giving it a try. The key it to provide evidence/documentations to convince the consular that your sister will leave the US after her authorized stay here. Some of these documentations might be proof of enrollment from college, proof of tuition payment (and/or housing payment), any scholarships she might have, proof of employment, if any, letters from college/professors, her grades, evidence of financial support from Nepal etc. that will prove that she has enough ties in Germany and thus higher chances of returning back after her brief stay here.

Additionally, if asked or situation arises, she should be able to tell the consular that she has everything to gain by returning to Germany and nothing to gain by staying in the US.

Good Luck to you and your sister.