Ungrammatical? "She belted most of a bottle of wine down before dinner had even begun."

She belted most of a bottle of wine down before dinner had even begun.

This is an example sentence provided for the entry on the 'belt down' in a Chamber's guidebook on phrasal verbs. And from what I have learned about Past Perfect, it seems to me that it is ungrammatical that 'had even begun' is in Past Perfect tense. I reckon it should be 'She had belted most of a bottle of wine down before dinner even began' instead. I know it is probably presumptuous to say this, but anyhow, I will be virtually over the moon if I got this right. 


Thanks


PBF

MH, could you highlight the structure of this construction so I know what to memorize?

My example:

She arrived before her mother had reached her hotel?

So I got it right in my example?

Don't you use the past perfect tense to talk about actions that occur before another past actions?


Thanks

PBF

Is my example correct? in case you didn't notice my previous post.

She arrived before her mother had reached her hotel?