hi there, if you want to bend her over for LST, then you could start with it, yes..
in regards to the stems turning purple: this can be genetics, or if it's in the stem it could be a magnesium issue, in case of magnesium i would however also expect to see more other signs on the leaves.. I wouldn't worry about it, unless you also see other signs.
if the leaves were turning purple, and not the stems it would most likely be a P deficiency..
happy growing