exiting U.S.A. before receing green card

[immihelp]

Dear Sir/Madam:

My sister got the immigrant visa to enter the U.S.A. Can she go to Canada and reenter to U.S.A. before she receives her green card or does she have to wait until she receives her green card?

Thank You.

[immihelp]

The day you enter the US on immigrant visa is the day you get your green
card. A stamp in your passport is your green card. You don't have to wait
for plastic card.

Read 'Temporary Stamp' at
https://www.immihelp.com/retain-greencard-useful-tips/