Question: I am planning to bring my mother in visitor visa to Germany for a couple of months. At the moment she is staying with my wife in Sri Lanka. Later I planned to file a hardship case and see if I can prove that she is dependent on me to try to bring her for a long stay. Because my wife will soon join me here and mom will be alone when that happens. She is 61 and widowed. She also doesn't speak the majority language in my country and is dependent on me for a living and she is emotionally dependent on me. So it'd be really helpful for her if I can bring her on a long stay.

Answer: 
It is always hard to predict how authorities will act, but I cannot see any good reason why it would make it harder for your mother to get a permit to stay with your wife any yourself in Germany if she had been visiting Germany once before.

I am sure you have already found the relevant information on the website of the Bundesamt für Migration und Flüchtlinge, aka BAMF, the German agency dealing with immigration? 

The basic information at <http://www.bamf.de/EN/Migration/EhepartnerFamilie/ehepartnerfamilie-node.html> says:

What they basically say is:

* You as the "head of family" who wants to reunite with his family members in Germany need to be able to sustain yourself financially and provide your familiy with money to live and with housing.
* Famility members who come to Germany need to have some basic knowledge of the German language, but there are exceptions to that rule.

So assuming you are in Germany on a legal base, have a permanent right to stay and work in Germany and you have a reasonable income, chances are you will succeed in getting your wife and your mother here.

Just one word of caution: It way take time. But back to your original question, there is really no reason why your mother visiting upfront would cause any issue.
I am not a lawyer, and this is not intended as legal advice, but [§36 AufenthG](https://www.gesetze-im-internet.de/aufenthg_2004/__36.html) says

> 
> (2) Sonstigen Familienangehörigen eines Ausländers kann zum
>  Familiennachzug eine Aufenthaltserlaubnis erteilt werden, wenn es zur
>  Vermeidung einer außergewöhnlichen Härte erforderlich ist. 
> 
> 
> 

A residence permit may be granted to other family members (e.g. parents of a grown child) of a foreigner if that is necessary to avoid unusual hardship.

* Someone who applies based on §36 would have to explain why it would be an unusual hardship for the parent to stay in her or his homeland.
* Someone who applies to a normal Schengen visa would have to demonstrate ties to the homeland and reasons why one would return.

To me this looks like a problem. First one writes that the parent wants to visit briefly and that he or she will definitely **return** afterwards. Then one writes that the parent would face unusual hardship if the **stays** home. If there is enough time between those two statements, they might look credible. Circumstances change. A mother may become more infirm. If they come directly after each other, they cannot both be true.