If she has had an Echocardiogram and the medications were prescribed by a veterinary cardiologist than I think that is fine for her to take Enalapril. I assume that in addition to the occasional heart murmur your dog has chronic cough and/or heart enlargement?
Doxycycline is an extremely safe antibiotic which is also occasionally used holistically as an adjunct to anti-cancer treatments, but it is a poor antiparasitic medication. There are far better medications, which are quite safe for lung parasites and include: Panacur and Drontal. Ivermectin is also used for some lung parasites, and although fairly safe, should be used with caution. Your doctor may have prescribed doxycycline for a lung infection secondary to lung parasites, and not for the parasites themselves.
I think that a definitive diagnosis is necessary, so your dog should be seen by a veterinary cardiologist ( if she has not yet been seen by one). The cardiologist can perform an echocardiogram, transtracheal wash, or other lung diagnostics to find parasites, bacterial, viral components, or fluids. Several types of fecal analyses can be performed to find lung parasite eggs or larvae, and a blood test can be performed to discover if there is eosinophilia (a blood parameter to detect parasites). Once the parasite is identified proper therapy can be instituted. Make sure that your dog is also heart worm negative.
A temperature of 101 to 102 is normal.
If the herbal formula has been prescribed by a veterinary herbalist than I am sure that it is a safe adjunct to her therapy. If it has not been prescribed by an herbalist, than it may take some trial and error before you find the correct herbal formula for your dog, especially without a definitive diagnosis. Herbal formula's can be used as an only therapy for innocent heart murmurs in which there are no other symptoms.