Train is going to involve at least 2 trains, since Cherry Hill is on the NJ Transit Atlantic City line, which doesn't connect directly to EWR.

If going by train, she'll need to either shell out for Amtrak to Philadephia (which can be quite expensive) and switch to the Atlantic City Line, or take NJTranist from EWR to Trenton, then the SEPTA train from Trenton to Philadelphia, and then the Atlantic City line from Philadelphia to Cherry Hill.

So car service will be much more direct, but probably quite a bit more expensive, too.

Two other alternatives:

1. If somebody can pick her up, she could take the NJTransit train from EWR to Hamilton, NJ, which is an easy 35 minute drive up I-295 from Cherry Hill. Or she might be able to arrange a car service or taxi from Hamilton to Cherry Hill, thus eliminating some of the cost of a car service directly from EWR, while eliminating the hassle of switching trains.
2. If she has a flexible ticket on CO, look into changing the destination to Philly instead of EWR. CO both flies to PHL and codeshares with Amtrak to "ZFV" (the Phila train station). If the ticket is a flexible ticket, it may cost less to just fly to PHL (which is quite close to Cherry Hill) or to take the CO/Amtrak codeshare to ZFV as opposed to buying a separate train ticket to Philadelphia. Of course, if she's arriving on LY or some other airline, this doesn't really help.