Although I don't think tripping every week is a good idea for anyone, I'd still be more concerned about someone drinking every week - which is rather common. It isn't going to make your friend stupid, or give them brain damage, but it may result in them being rather physically and mentally worn out until they give it a break for a while, which can result in them not thinking quite as clearly - including memory issues like you mentioned.
The good news is having done worse than that, and tripped every 3-4 days for many months in a row at one time, I can say that simply stopping and taking a break alleviates all those symptoms completely, so they're certainly not permanent.
I think the biggest worry that your friend might care about is the fact that her trips will quickly become less meaningful and insightful due to tolerance build up - if she really wants to trip often she should keep it to every 2 weeks. Ideally you should trip no more than once a month if you want to keep 0 tolerance and have your trips as magical and intense as when you first took psychedelics
You should tell her this, and the fact is, if she at least takes a 2 week break between each trip, it'll be much more deep and fun, without many of the short term side effects! :D