Gosh I've never had this kind of problem! Sounds like she's frightened of the leaving for a walk set up.
You could try to desensitise her to the lead and the coat by leaving the lead out somewhere where she can sniff it, watch it and get accustomed to it, and also hang your coat on the back of a chair or something so that again she can have a good look at it at her leisure. Put your coat on intermittently during the day doing normal things, like walking out into the garden or sitting down and watching tv. Don't force her to go for a walk if she really doesn't want to as you'll just compound her fear of the situation. Break down the frightening components into bitesized pieces and reintroduce them to her slowly and with a lot of praise when she accepts them as being okay.
Maybe even play with her on the floor with the lead and treat her if she happily goes up to it.
If she's frightened of the lead being clipped onto her, then sit on the floor with a handful of tasty treats and when she's snuffling some of those clip the lead onto her, if she's unhappy about it then unclip it and try again a bit later.
I'm sure she just needs some re assurance about the whole set up, so break it down for her in a friendly way and let her investigate each different thing seperately so that she doesn't get overwhelmed by it all.
Good luck with her
Mary xxx