Can you talk to your old trainer? It sounds like she gave you some nice opportunities and could put in a good word. I would ask her if she has suggestions.
If she doesn’t I would start as a once a week lessoner to get back in shape and find a barn and program you like. Then put together a resume with some references from your old trainer and people who know you’re riding level and send it out to barns in the area as well as talking to the trainer you will have been taking lessons with.
I agree that a part time job somewhere else might be the way to go, but in the mean time while you’re getting fit again it can’t hurt to try.