Nice shape & color. It looks like a viburnum but I can't say which one.

Physocarpus opulifolius 'Diabolo'

The leaves don't look right for Physocarpus they look like a hazel so Corylus maxima Purpurea would be my guess.

Yep,Corylus, as Jimmy says - it will just keep growing, no matter how many times its cut down, the majority of plants do. It needs cutting down and the base of the woody stems need drilling into and SBK applying to them to kill it off. If its been cut down many times, unfortunately, there will be lots of thin woody shoots off the main stem at ground level now, so digging around to find a central large root or stem to treat, as well as the others, is probably necessary.

It the flat is rented your friend needs to check with the landlord before she kills it though. Wild corylus often used to be cut right back (coppiced)regularly. This encourages the growth of new long shoots when were then cut and used for various purposes. So its not surprising that your tree recovers so quickly - that's what they do. The word "copse" derives from this practice.

Thank you everyone. I will pass this on to my friend.