Yes, she can because there is Ijma (consensus) that it is permissible to have intimate relations with slave women, even without marriage, and hence by consensus there is no 'awrah of a slave woman in front of her master هـ, because it follows logically from that permission.
This is proven in the Quran, where they are mentioned besides and separately from wives:
إلا على أزواجهم أو ما ملكت أيمانهم فإنهم غير ملومين
Except from their wives or those their right hands possess, for indeed, they will not be blamed -
— Quran 23:6
فانكحوا ما طاب لكم من النساء مثنى وثلاث ورباع فإن خفتم ألا تعدلوا فواحدة أو ما ملكت أيمانكم
Then marry those that please you of [other] women, two or three or four. But if you fear that you will not be just, then [marry only] one or those your right hand possesses.
— Quran 4:3
It is also proven by the practice of the Prophets Abraham, David, Suleman عليه السلام as well as that of the Prophet Muhammad ﷺ who had relations with his female slaves: Rayhana and Maria without marriage. The same has been practised by the Sahabah: Ali bin al-Husain ibn Ali, Qasim ibn Muhammad ibn Abi Bakr, Salim bin Abdullah ibn Umar were among the well known children of the Sahabah from Umm Walad slaves.
To insinuate that all of these people and generations after generation of Muslims have misunderstood the Quran and erred, and that you have understood it correctly, is not credible and is equal to negating the statements of the Quran itself (see 9:100, 3:110, 4:115).
Regarding the verse of the Quran that you have asked about:
ولا يبدين زينتهن إلا لبعولتهن
... and not expose their adornment except to their husbands ...
— Quran 24:31
The word here is بعل (Ba'al) which can mean both husband or master. See Tafsir al-Qurtubi:
التاسعة : قوله تعالى : إلا لبعولتهن والبعل هو الزوج والسيد في كلام العرب ؛ ومنه قول النبي - صلى الله عليه وسلم - في حديث جبريل : إذا ولدت الأمة بعلها يعني سيدها ؛ ...
مسألة : فالزوج والسيد يرى الزينة من المرأة
Ninth: The Saying of Allah "except to their husbands", البعل is the husband or master in the speech of the Arabs, as in the hadith of the Prophet, the hadith of Gabriel: "when slave-girl gives birth to her master" (source: Sahih Muslim) ... The husband or master can see the adornment of the woman
From Edward Lane's Arabic-English Lexicon:
From Brown-Briggs Hebrew Lexicon:
So, the owner of a believing slave woman is among the people who have been granted the concession.
هـ An exception is where the original owner has married off the slave to another person. In this case the owner can not see her private parts, nor have relations with her, and her ruling will be similar to that of a mahram.