Lady Hermon has said she expects to meet Prime Minister Theresa May face-to-face to discuss her potential support for the draft Brexit deal.
The Independent Unionist MP said she needed personal assurances from Mrs May before she would vote for the EU withdrawal agreement in the Commons.
Lady Hermon told BBC News NI she was "not happy with everything" in the deal but there was no time for alternatives.
She added that having no deal at all would be more damaging for unionism.
The North Down MP, speaking to the Inside Politics programme, described the prime minister as a "committed unionist" and said she did not believe she would strike a deal that risked Northern Ireland's position within the United Kingdom.
However she added: "There are things I need clarification from the prime minister herself. I need her to look me in the face and say 'don't be worried about that' or 'I can guarantee this'.
"I need assurances from the prime minister before I will finally give my vote to this particular deal.
"However, I would be very surprised if I were ever to find myself on the same page as Sammy Wilson and Jacob Rees-Mogg."
Lady Hermon said "every vote will count" when MPs give their verdict on the agreement and confirmed she was "in discussions" with Mrs May about setting up a meeting.
The MP also rebuked the Democratic Unionist Party (DUP) over their response to the draft Brexit deal and called on them to "tone down" their rhetoric.
DUP deputy leader Nigel Dodds had criticised Mrs May's deal on Thursday, claiming it would make the UK a "vassal" state and lead to the break up the union, while DUP MP Sammy Wilson compared the agreement to a "punishment beating".
The DUP is unhappy about the border backstop, an insurance clause to protect an open border on the island of Ireland, which if enforced, would see Northern Ireland more closely tied to the rules of the EU single market that other parts of the UK.
But Lady Hermon said she believed that no deal would automatically lead to a hard border on the island, which would be exploited by republicans to push for a referendum on Irish unity.
"I have to say I have found language being used by senior members of the DUP extremely upsetting and concerning and I think they just have to think of the implications of what they are saying," Lady Hermon said.
"Words like vassal state, words like betrayal are very upsetting, they're very dispiriting and they cause great concern right across Northern Ireland."
She told the DUP that they should remember the prime minister's commitment to British unionism.
"Theresa May is not going to jeopardise the constitutional status of Northern Ireland within the United Kingdom, that is just not in her make up at all," the MP added.
Lady Hermon voted remain in the Brexit referendum but said there was not enough parliamentary time left to strike a new deal, or hold a second referendum.