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 dont 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 thats 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