I can empathise with you, I too have an anxious dog!
Desensitisation is the key in these situations. This allows retraining and rewiring of behaviours which have become habitual. I would also recommend visiting your vet to discuss the use of tricyclic anti-depressants as a training aid. The anti-depressants are not sedatives and actually assist dogs during the desensitisation and retraining period allowing an easier transition to improved behaviour through increased responsiveness to new commands.
A DAP collar may also be helpful as may a thunder coat, both act to decrease anxiety. I would recommend joining a reputable dog training class where your little girl can be in controlled contact with other dogs and learn to ignore them and concentrate on commands instead. If she is food orientated this will be very helpful! Also make sure when you do take her out that you aren’t transferring any anxiety to her – dogs are excellent body language readers and the slightest bit of tension in us is quickly picked up by your faithful furred companion! This sort of behaviour is reversible but it does take patience and retraining. I wish you the best of luck!