Answer:
Wealhtheow is Hrothgar's wife, the queen of the Danes. She married him as a peace offering - it wasn't her choice to get married to him, but because her nation was fighting Hrothgar's, she had to sacrifice her own wishes and desires in order to stop the potential war. That's your first indication of her being subservient - she listened to what others told her to do and then did it.
In the passage, we see her arriving at the banquet gracefully to offer her husband and the heroes the cup to drink from. She is a beautiful lady whom many respect due to her grace and gentle ruling as the queen. However, she is subservient to her husband, meaning that she has to listen to him as she is his wife, and he is the king.
Wealhtheow is the archetypal example of a gracious, yet subservient woman who can be seen throughout history and literature in characters such as Penelope from The Odyssey, Draupadi in The Mahabharata, etc.
