Re-socializing my beagle after a pittbul attack :(

Two weeks ago, my 1 year old awesome, fun, playful beagle was attacked by a pittbull on a walk in our neighborhood. It was quick, and it looked a lot worse than it ended up being - she only got one bit mark in her back. I took her to the vet and they gave her an antibiotic and some pain medicine. The cut healed fine and she's been acting totally normal at home.

The only problem is that now, when I take her out on walks, she gets really defensive whenever we encounter people. She used to be playful and social, and she'd wag her tail and get super excited to have people come pet her. Now, she stands very attentive with her tail straight up, and the hair from her neck all the way to the tip of her tail stands up like a mohawk. We've had her since she was 6 weeks old and she's NEVER done that! If people come close, she barks (not a playful, excited yip but an aggressive bark that she also never had).

I want to re-socialize her. I think since she is only 1 year old and had such a great personality because before she was attacked, this shouldn't be so hard.

As I said, she is still this way at home with my husband and I, and also when our family comes to visit. It's only when we are out walking and we encounter people that she gets aggressive. We haven't encountered other dogs on our walks yet, but I am worried about how she will respond when that happens. I did try taking some treats on the walk with us and I tried giving them to her when we passed others to distract her from them, but she was not interested in having a treat until we got home haha

Any advice you could offer me would be greatly appreciated!