You have gotten some good advise. It is going to take time to help her get over her shyness of people. Keep working on it. Here is an analogy that might be helpful.

If you are terrified of spiders and someone came right over to you that you didn't know well, while your trusted companion was holding you and put the spider on your head - how would you feel? Would it help you get over your fear? It is pretty much the same as having a person you don't trust loom over you (we are much taller) reach down and pet you.

Patience is needed. If you could enlist your neighbor in some exercises. Be in an area where Sesh feels comfortable and can be off leash. Make sure he is a distance away where there Sesh is feeling comfortable. Have the neighbor with very good treats (chicken, hot dogs, pieces of steak) in his hand. He should be sitting or crouching down and completely ignoring the dog. Have him toss treats (not throw - the overhand motion could be intimidating) in the general direction of Sesh, while looking the other way. Little by little let him increase the distance between them (small increments) until she gets more and more comfortable. Eventually she will approach him and allow him to pet her. When this happens (and it could take weeks) make sure he pets her under the chin or on the chest, not over her head.

The reason the walks are not working is she is probably too close and she is restrained - her anxiety level is too high.

Good Luck