Yes it is unless there's an action/verb (instead of the copula "to be"). For example: Cô ấy đã từng ăn uống với tôi = She used to dine with me.
In THE VERY SAME SENTENCE in this module, if you answer this above it gets marked wrong--it enforces 'người bạn'. In this exercise, the opposite is true, if you put in 'người bạn' instead of just 'bạn' it gets marked wrong.
Again, we could fix this problem if we were empowered to do this. This has been going on for two years with no fix.