Make it enjoyable, coffee stop, lunch in the dry nice B&B weekend or hotel with dinner etc etc etc Its not rocket science. Hire a decent full sus. I took my daughter to CyB. Never ridden MTB before. Hotel, good food. First day was tution on site on hard tail by local trail guy. Basics, blues, cornering braking etc I also joined in the class too. Second day I hired her a full sus and we together we did some more blues then a very easy short bit of red. Lunch in cafe etc etc She never fell off and has since converted to MTB.
Not in the rain, mud, crap hire bike, freezing cold, no tuition. Not as a first ride. TBH the issue is with you and taking someone out in challenging conditions. I’ve seen this approach (sink or swim) a few times it dosent work. Once she’s intrested then suggest you both go on a days tuition – its not for you its for her – be there and enjoy it.