Should I ask for a recommendation letter even if I have not applied for any programs yet
Definitely, you should tell her that you would like to further your training. And since your former tutor know you well, she is one of the capable person to write this letter. 

Meanwhile, she doesn't have to write it now and then - if you manifest the possibility of asking her in a near future for such a letter and she agree, this will still stand in a year or so. 

It is hard to write a good and relevant letter in advance without knowing on which desk it will land on - so better make precision when you know more details, such as the institution, concentration, which possible supervisor, with hyperlinks to relevant pages in case she want more context.