In theory, yes. She may receive greater-than-average scrutiny when she reenters the US. If she has specific plans for a short stay and a flight already booked to take her out of the US at the end of that stay, preferably to a destination outside North America, she will probably be fine. Still, there is a chance that she could be denied entry.
She could also submit a change-of-status application seeking B-2 visitor status. This is rather more expensive ($370), but essentially guarantees that she will be able to join the family on the vacation and attend the wedding because these applications take weeks or months to decide, so there's no chance that it would be denied before she plans to leave anyway.
I should call attention to the warnings offered in several comments:
I disagree with the filing change of status part. Since the change in policy last month, a denial of a change of status leads to being immediately put in removal proceedings. Even if by the time this happens she’s already left the USA, on her record it will likely be annotated that she was in removal proceedings. That will likely lead to massive problems at her next entry. Applying for change of status or extension now is not recommended unless under absolutely necessary. – Musonius Rufus
@MusoniusRufus can she not withdraw the application if she leaves before it is decided? – phoog
You are aware that USCIS and ICE are not fully integrated. Also from my own experience I know one can file additional paperwork for a petition and it can be sitting somewhere with them while the original petition is adjudicated without them reconciling the two. So yes she could file to withdraw but by the time they enter that into their system the original petition could be adjudicated and her put in removal proceedings with them not realizing she had already withdrawn it. Of course she can go on and have it corrected but will she even know until she tries to come to the USA next time? – Musonius Rufus
USCIS & ICE are notoriously incompetent and siloed and can be doing things related to the same person without talking to each other or updating each other about developments. I would not risk it. – Musonius Rufus