Rescue Dog Aggressive with Child. At a loss.

Okay. We adopted our beagle mix 4.5 years ago. She was 7 months old and had been in 7 homes. We knew she had trust issues and were determined to work with her.

In the first year, she nipped two different people. We had a behaviorist come in and agree that when people come to visit she should be put up. Lilly gets very stressed around new people because she was never socialized properly.

Fast forward. No real incidents over the next 2.5 years. Then we had a baby. Lilly was very jealous of the baby from the start, and I was apprehensive, but we kept working with her and seemed to make great improvements.

Baby is now 9 months. Every time she tries to get to me when Lilly is around, Lily growls and trots off. Last night, Lilly lunges for the baby.

I don’t know what to do. We live on teacher salaries and can’t really afford in home training. We could keep Lilly in a separate part of the house, but that wouldn’t be a good life for her. We could muzzle her all of the time, but again, that isn’t a good life. We could take her back, but she would have serious behavior regression, plus that thought is killing me.

Thoughts? Advice?