It was never a question of intelligence. Of course she could choose whatever she wanted in college and succeed at it.
I agree completely with Cafe. It's not so much that I don't have the ability or intelligence to succeed at whatever I choose as that I don't think a job is that important to overall happiness. A job is a job, and probably no job is going to be sunshine and roses. So I think it's less important that you cultivate a job than it is that you cultivate a happy homelife, friends and family, and hobbies and pastimes that you enjoy. It's the things going on outside of your job - the people you love and the things you do in your spare time - that make life worth living. So I'm not that motivated to find the perfect job or pick the perfect major. Besides, 70% of people with college degrees don't have jobs related to their major. So I figure I'll take the major that is most enjoyable for me, and see where I end up. At the end of the day, a cool job isn't my goal. My goal is to make my overall personal life enjoyable, and to have the friends and family and inner strength that support me when my career is rocky or going down the drain.
By the way, raising children takes all of your resources and is probably 90% mental, 10% physical. You see perfectly able-bodied parents in their thirties doing nothing for their kids. There's a drug king and queen living down the street from my dad who don't know how to take care of their kids; physically they could, but they don't know how, because they're not mentally or psychologically strong enough.
Raising kids... I just don't know how people do it. Kudos to you, Cafe.
Anyway, back on topic. As an INFP, I'm not like this. She sounds like she's overall unhappy with herself and her life right now. She may be striving for an ideal, like others have mentioned. Have you looked into her enneagram type, by any chance? That might provide you with a lot of valuable insight into her motivations.
I find that when I feel good, I just naturally make good decisions for myself, and that means that I can have the insight to plan, if need be, and to make tough calls (T and J). I think people may be focusing too much on MBTI theory here. People really are adaptable and can make good choices that seem to involve their "weaker" functions. For this INFP, maybe she just needs a boost of confidence and self-esteem. She seems to depend too much on outward circumstances to make her happy. I think to be happy in life you have to find something inside of you that sustains you when all else falls away, as it often does. Maybe she needs to be reminded that shit can happen and she can still be happy. In fact, shit will always be happening. She can be in pain and acknowledge it and still be happy.