Sit her down at nexstitch.com and let her watch various stitches being done, just tell her two watch them a couple of times over and over. Some people who have been "bullied" but someone who is a strong personality , kind of Shutdown when talking to someone or trying to learn because they get a mild "people phobia". Take her to your computer and let her just spend time watching ( with a cup of tea or coffee, or pop , so she can relax) make sure she knows how to click from one video to the next.
The website has crochet section from basics up and a Tunisian crochet section. Tell her to just enjoy watching and leave the room, because she may be "up tight" around you too.
After she's had her video session, have a tea quietly with her no crochet hooks, have a "fun" gab about weather , the tea whatever, when she loosens up a bit ask about her health does she have any minor aches and pains, dry hands ....it all affect "how you crochet" , some people don't like the "bound feel of wrapping the yarn around the pinkie finger, you might suggest she just let it glide between the third and fourth fingers.
You'll likely find that she is having a problem with how tightly she is holding and doing her crochet, (that is likely why the relative suggested the big needle) But what she needs is to relax and be told "she is smart",
"very capable of learning" "everyone is slow at first" (tell her a stories of how you "goofed up" when you first started. She needs to learn to be comfortable around her "teacher" and confident in herself before she can learn. If she does something wrong talk to her softly and encourage her gently. (make sure when you encourage her that you don't make her feel like a half wit.) Tell her stuff like you don't learn over night it take a while but if she keeps "patiently trying" she will be making beautiful and gorgeous things in no time. (Except there wasn't any computers when I learn, that is how the elderly lady taught me.) When she first tried she quickly learned if she sounded impatient or out of humour that my listening just "shut down". I had had alot of bullying, criticizing and ill humour then.
She was patient, quiet and encouraging. We became best of friends and I learn crochet with great relish and joy and new found confidence. Your lady sounds alot like me at first. My teacher was kind and wise. Hope this helps you both. You have a good heart to keep trying. Crochet is likely exactly what she needs.