snowberry is like that. If it didn't make me sound like a madwoman I'd say "Kill it!". But as it does, you might have to prune it really fiercely.
And think of something to replace it with while you decide whether or not to take up my psycho suggestion! Mallow is pretty and hardy, but it does tend to get a bit out of hand too, and needs chopping right back almost to the ground quite regularly. If it's ground cover you need rather than something tall, then alchemilla mollis (lady's mantle) grows quickly, looks after itself and isn't very tall.

Its spooky isn;t it when you know instinctively that you should say "goodbye"
thanks Sunnyfunny you have confirmed it for me, I will do the dirty deed...