If you take a look around the forums, you'll find that heart murmurs are actually very common in puppies. In most cases, they're entirely innocent and the pup just grows out of it. A grade 2 murmur is mild - classified as "A soft murmur that is readily evident". You can see the grade classifications and more information at:
http://www.offa.org/cardiacgrade.html
With a grade 2 murmur at 14 weeks, it is perfectly likely that it is innocent and your pup will just grow out of it. Not guaranteed, of course, but likely.
The best thing to do would be to give your pup a bit more time, and review things when she reaches at least 6 months (and if it's still apparent, then again at a year old). If the murmur is still clearly detectable, then you need to have her looked at by a Board Certified Cardiologist (not just a standard general practitioner vet).
Do do a search of the forums here - there are plenty of threads on heart murmurs that will give you more information, and quite possibly a bit of peace of mind
