Velkommen Signe, since you had to stop to care for the baby, I will ask some questions.
Since your friend is opposed to things that are edible, something like boxwood, yew, osage orange or catalpa would be decent choices.
There are lots of fast growing
trees that she might find suitable such as poplar, cedars, hollies, or spruces.
On our
land, cedars grow about 1.5 meters per year once they establish (aprox. 2 years of growing in ground)
It is too bad she doesn't want edibles, mulberry grows at almost 3 meters per year after the first year, has the ability to reach deep for
water so you don't have to water it so much and they spread their branches as quickly as they grow.
Redhawk