入境章應該可以

7 USCIS-PM B.2(A)(2)說：

“Evidence of Admission

An Arrival/Departure Record (Form I-94), including a replacement when appropriate, is the most common document evidencing a noncitizen’s admission. The following are other types of documentation that may be accepted as proof of admission into the United States:

• Admission stamp in passport, which may be verified using DHS systems;”

其實你母親這個類型隻需要證明她合法入境。合法入境的定義就是移民官看到她而且讓他進入。就算她沒有入境證件或移民官沒有給他身份也是算合法入境。入境章就足夠證明移民官看到了她而且讓了她入境。所以足夠證明合法入境。

如果真的要入境記錄，可以做FOIA request。但是這個會耽誤時間。