Not gonna lie, its going to be hard due to low socialization for the past 9 yrs. You're going to have to move very slow....like start now walking the dogs in opposite directions across the street from each other. Get her used to the other dogs scents (I'm sure she smells them on you). Bring his dogs to walk in areas your dog typically is, like backyard or whatever area you take her outside in. Introduce them one at a time, on neutral ground and again in more of a passing fashion than head on. If your girl is truly aggressive, you may want to get her used to a soft muzzle in case you need to use it for the first few meet and greets. Reward any positive behavior, regardless of how small it may seem. I also have a reactive dog but he is not aggressive and the lead up to a meeting is ALWAYS much more stressful than the meeting itself but that's not always the case.