Aww the poor sweetie. I've cared for dogs that are really scared of everything like that. It can't be fun for the and can be stressful for you. My biggest recommendation is to get a behaviorist - a trainer who specializes in helping high-anxiety dogs. You can do some research on the internet or ask around for advice in your area. Meet the behaviorist and let him/her interact with you and your dog before you commit. Many will do a free consultation or do an assessment for a discounted rate. In the meantime, here's some other things you can do:
Contact your vet and let him/her know the situation. They may be able to advise over the phone.
Provide her with calming treats, aromatherapy, or natural calming aids. You can try CBD treats (smaller pet stores usually carry them; they do not contain THC so your dog will not get high), or other calming treats you can get at any pet store. Valerian or melatonin can be added to her food (they are "sleep aids" but in small doses can help calm anxiety); some calming treats have these in them or you can buy them at a health food store or online. I recommend high quality. If you have a diffuser you can get lavender, vanilla, and/or orange essential oils and place a few drops of one or a combo in the diffuser to scent the room. Or you can mix one or more of those oils (just a drop or 2) with a carrier oil like Coconut and rub a little down her back or paws. There are other oils that are calming but those 3 seem to be the most pleasing for dogs.
You can try a thunder shirt; those can be very calming.
She's older, past the ideal training, but you can work on training her. I know you can't right now, but when the pandemic is over, ask a friend to come over, preferable female adult, that your doesn't know. Instruct her not to approach the dog when she arrives. Give her a couple treats when she gets there. Have her socialize with you, ignoring the dog, unless the dog approaches. If it's been a while and the dog doesn't approach, ask your friend to sit on the floor with her back to your dog. Lay a trail of treats to her and see if your dog approaches. This could take time and maybe several visits. Once your dog approaches, your friend should offer her hand, palm down, to sniff. After the dog has poked your friend's hand with her snout she can gently try to pet under the chin or chest (not the top of the head). After your dog is used to that friend, or if it's been a few hours or day since she was there, invite another friend and repeat the process. Just slowly introduce her to adult females who are calm and will respect her boundaries. I'm sure you want to ... (more)