My friend is Iranian and she would like to visit Nepal for a month... how can she get a visa ? from where ? and which is the cheapest way to get there from India ?
Waiting for your reply...

My friend is Iranian and she would like to visit Nepal for a month... how can she get a visa ? from where ? and which is the cheapest way to get there from India ?
Waiting for your reply...
Nepal embassy Delhi offers visas. Check online using google.com : "tourist visa government of Nepal" to see if she is eligible to get one at the border. I recommend train to Gorakhpur, then bus to the border and of course bus onward, tough travel. Otherwise fly in..
I presumed she planned to overland through India. Given the length and expense of overlanding it might worth considering a flight..

Nepal has arrival visas at the airport for some nationalities ($30 or so). Similarly, getting a visa in Delhi may not be required. However, requirements for Iranians maybe totally different.
Check with the airlines. Because they are liable for penalties and must remove anyone denied entry, they try to maintain accurate information. There are several online sites based on a master "IATA" visa database.
For example: Delta Air - Planning/Visas

From the Delta Air website:
Nationality: Iran; Destination: Nepal; Via: India
Passport and visa required.
Tourist visa can be issued on arrival for a stay of:
- 60 days, fee: USD 30.-;
Fees to be paid in USD or equivalent in convertible currency.
Best wishes.