So she was there praying with the rest. Big deal. I would expect her to show up.
Mary was amongst the people the Holy Spirit descended upon the day of Pentecost.
I repeat, with all the others. She wasn't special here either. The rest recieved the Holy Spirit as well.
What's your point?
Are you kidding me? How many other people that day DID NOT receive the Holy Spirit? That would be everyone else in the world. Other than the Apostles, she is the ONLY one NAMED out of all of the people who were present. This is displays some significance. This may not seem like a big deal to you, but it is. Whoever continues to discredit the Mother like this (i.e she is just a vessel, she's not "special") insults the Son.
In Acts 2, the Holy Spirit only came upon the 12.