before even thinking about putting a saddle on which I am glad your hestiant about ... I would focus on a few of these
- getting her desentized to grooming and being touched everywhere
- then work on picking up feet
- then desentize her to blankets , tarps, bags, anything and everything you can touch her with and take off and shake around her until she is no bothered by it
- then work try to do some lunging... you don't need a pen to teach her... it does help but you can do it without...
- once she goes good on the lunge I would introduce the saddle and saddle pad but not get on... just work her in it
And so forth but that's the short version and I left alot out... but until she allows you to touch her everywhere she is techincally unsafe because she is not ready for anything else imo
Goodluck I hope you can find a knowledgeable person to help you other than your brother in law