In chapter 7 it becomes apparent that Daisy, while she might love Gatsby, isn't going to leave Tom. As Gatsby and Tom are having their huge confrontation in the hotel room over Daisy's feelings, Daisy is just sitting there in a kind of shock. Nick as narrator explains, "but with every word she was drawing further and further into herself, so he gave that up and only the dead dream faught on as the afternoon slipped away, trying to touch what was no longer tangible, struggling unhappily, undespairingly, toward that lost voice across the room." Then it is revealed that Daisy's "voice begged again to go." And she says, "Please, Tom! I can't stand this anymore." It is important to note that she is pleading with Tom, not with Gatsby to end the discussion. It is obvious that she is still connected with Tom at this point. As chapter 7 comes to a close and the death of Mrytle is revealed, it is very significant that Tom and Daisy are in their home, sitting together over uneaten food, and seeming to be getting along just fine. Nick says that it doesn't even look like they are conspiring, and he feels bad that Gatsby is staying outside to make sure Daisy is OK, but that he is really just "watching over nothing" because Daisy and Tom aren't going anywhere: Daisy isn't leaving him; Tom is leaving her or blaming her or anything else.
In chapter seven of The Great Gatsby, Tom finally finds out about Daisy's affair with Gatsby. For Gatsby, this is a pivotal moment because he believes that Daisy will tell Tom about her intentions to leave him. But, as Gatsby and Tom argue, it becomes apparent that Daisy has no intention of leaving her husband, and this is shown most clearly by the following quote:
Her frightened eyes told that whatever intentions, whatever courage, she had had, were definitely gone.
This demonstrates the extent of Tom's hold over Daisy: she has lost her will to leave and start a new life with Gatsby. Moreover, Tom's hold over Daisy is not based on love; it is based on her fear of what leaving him would mean for her socially and materially. When Tom sends Daisy home with Gatsby, she dutifully obliges, proving that she will never leave Tom for Gatsby.