Schuldnerberatung

Has your friend contacted the landlord to come up with a payment plan?

There is debt advice in almost every city. Just type in the city + Schuldnerberatung on Google. It's free.

Many indebted people are ashamed of their situation and thus keep it to themselves.
However, this is normally the wrong course of action, as it makes things worse.
For example, a landlord can (and probably will) terminate an apartment or room rental when the tenant is two months behing in paying rent. But he/she is less likely to do so if the tenant pro-actively approached him/her about the problem - and once a payment plan is agreed on, no termination is allowed any longer.
The situation is similar with debt to banks, companies, private people, etc. - any attempt by the debtor to find a solution (even if unsuccessful) is seen as positive.
Debt counselling (Schuldnerberatung), which is ofen offered by charities and public offices free of charge, is a very good first step in sorting the mess and finding a way out. Your friend should google the ones in his/her area and visit one ASAP!

Thanks for the advice, she has already approached her landlord about a payment plan but they arent very agreeable and by the end of this month want all three months rent at once. Which is practically impossible for her.

It is the landlord's right to get paid in a timely manner - any other arrangement would be goodwill (which seems to be lacking here). Since non-payment of rent is one of the very few grounds to terminate an unwanted tenant in Germany, she should definitely pay - or be prepared to move out.
Debt counselling could help her to find a way out. She should get one ASAP! (In fact, she should have done that when the first rent could not be paid!)