Hi. There is the book - an old standard - "Raising Ophelia", which i believe mentions the fact that not only is it normal but also extra important for a daughter/father relationship to be more connected at ages 11-13, because it is where the healthy idea of man/woman relationship gets embedded. If girls aren 't bonded with dad by that time, they likely will never, and may have unhealthy ideas of relationship or themselves moving into adulthood.
Studies show that the cues they get from Dad at that time are triply informative as they move into their adolescence and early adulthood, choosing mates etc. Dad's are supposed to not only provide strong support in the way of listening, laughing, discipline-giving and teaching, but most importantly cue their daughters as to self-image: if Dad tells daughter she is beautiful, worthy, smart, approved of, valued, and attractive (likeable, worthy) to him, and if he gives the message that she's worth a lot of respect and should value herself - if he does all this especially during these ages, daughter will form a positive self-image. She needs DAD to tell/show her this approval and support because she will be forming a relationship with a man as she moves forward (unless of course she's gay, but even then the traditional cue-giving can be more trusted if coming from dad). Mom is discounted precisely because daughter identifies with mom. It's like ask herself if she's worthy. She doesn't know and Mom doesn't know. They are one in the same.
Finally, Daughter needs to differentiate in order to survive in life. At puberty girls begin to know they aren't actually their mothers and they know intuitively that they will partner with others in the world, probably men, so that male perspective and succeeding with that heretofore unknown counterpart becomes a matter of survival essentially. Moms should smile and be proud if their daughters are stretching away for this time from their old Mother/Daughter closeness because it signals appropriate development; something daughter would not be confident enough to do if mom hadn't already provided so much security in their relationship. And no worries of course, because moms are important for life.
Mom will regain her daughters ear/interest the more mom can hang back without checking out or getting insecure herself. Smile, be proud and supportive, don't take it personally, stay interested and trust trust trust...daughter for life. :)
here are some resources for your friend - books that talk about Dad/Daughter relationships:
Girls Will Be Girls: Raising Confident and Courageous Daughters by Joann Deak (Paperback - Aug. 20, 2003)
Buy new: $15.99 $10.87
Just Dad and Me: The Fillin, Tearout, Foldup Book of Fun for Girls and Their Dads (American Girl) by Stacy Peterson and Erin Falligant (Spiral-bound - Mar. 1, 2010)