Yes it is.
it is braj bhumi. girls are always get resect their. during holi festival u got lots of solo travlers . u'll find indians , nris , and non indians too. u ll have lots of fun there. just go for it.
It is safe but you should be careful enough not to tell anyone that you are travelling all alone.I believe the place will be safe but now a days nothing is safe for women we should be careful with each and everything.