Generally, and I'm sure other Dermatologists would say this also, the first dose of approximately 25 units is quite reasonable and will be in the ballpark for many younger women for the forehead and frown lines.   You mention that she added 60 more units over a  2 week period.   I'm wondering if this is correct since this would be an exceptionally large dose.  Please be sure you going to a board certifed dermatologist???  (Here is more info on finding good providers)

I sincerely hope she's not diluting her Botox too much.   Here's what I often tell my patients if they truly have that '11' groove.  Your muscle there (the corrugator) has been over active for a long time.  It won't relax completely in one treatment.   As you continue your treatments, you should see continued improvement up to a point.  If after 3-4 Botox treatments about 3-5 months apart, there is still a deep line.  A tiny amount of HA filler(experts only please), can be placed underneath the line to 'pop it up.'   Remember Botox lasts longer gradually.  Often the first follow up is at 3 months, the second at 4 months and then often every 5-6 months is sufficient for a younger patient.   Hope this helps.  Dr. I