Baltimore City Jury Summons question - postpone now or in person?

So my sister got their first jury duty summons for May. She is available on the 26th (summons date) and filled out the qualification online but she knows she will be on vacation starting the 27th. Would she schedule a postponement now in advance or if she is summoned for the 26th, and it is not a one day trial but rather something needing her attendance for a week or two, would she then tell the judge that she cannot make it for those dates as she will be gone from the 27th to 30th (her friend is getting married, she already has transportation tickets and hotel reservations out of state).

Technically she *is* available on the 26th so postponing the summons date as vacation would not be truthful exactly? It's just the latter dates that week she would not be physically present to be there and be a juror. Does the judge typically allow vacation as a reason to be dismissed? Or should she just do the postponement now online to a later date? Sorry I am not familiar with Baltimore city and she doesn't have a reddit.