Which city to choose for German homestay and language course?

[MsFogi]

DD is going to Germany over summer and has the choice of the following places to stay (she'll pick two), can anyone with knowledge of Germany tell me where you would send your 17 year old DD (alone) to learn German - so I am looking for an idea of which of these towns/cities would be fairly safe and trying to find out which speak German that is not particularly regional (ie that DD would understand/is learning at school). She'll be staying in a homestay and when not doing language classes will be free to spend her time visiting the area and she hopes to find a library to do some work in whilst there. So the choices are:
Berlin, Cologne, Freiburg, Hamburg, Heidelberg, Lindau, Munich, Munster, Radolfzell or Regensberg.
Many thanks!!

Freiburg or Heidelberg are both beautiful compact cities, I’ve found them to be friendly and open. I spent some time in both as a student very many years ago and loved it.

No debate ... Munich! My DS did his year abroad and post-grad there. Very safe, good climate, excellent public transport. Expensive though. Hope she enjoys it.

I LOVE Munich, which is where I did my year abroad - safe, lots to do, gorgeous weather in the summer with lots of parks and natural swimming. However, the language spoken there is closer to Austrian and I barely understood some people even after 8 years of study - it can be a mixed bag. If that is something she is nervous of, I would go to Berlin, Cologne or Heidelberg, all of which are also great. Berlin in particular is fantastic.

For Hochdeutsch, Hamburg definitely.
Munich is lovely but is southern and is not the German she'll be learning at school.

Thanks so far for all the replies so far - I really appreciate you knowledgeable MNers, I don't speak a word of German but somehow DD is in love with the language so your wisdom is so helpful!

would recommend Heidelberg, Freiburg, Regensburg
These are beautiful little university towns, similar to Cambridge or Oxford but better weather. Very friendly, safe and small, she can easily go out and about there by herself. Hamburg and Munich are great but they are big cities but it will depend where exactly she is staying, how central, she will need to use the tube to get around town and so forth. For a first stay, I would go for a lovely cozy Southern university town.