Originally Posted by
EWG
Size small makes me think she's 5'-6" or less. Here are my suggestions:
No ebike for the reasons Toast mentions - cost, resale, commitment, partner. Get a lower travel full suspension that will work for a smaller person. If she is 5'5" or above, any wheel size is fine. 5'4" or shorter, consider 27.5 wheels or a mullet. No hardtail, as that will make her pretty unhappy riding what her BF wants to ride.
Santa Cruz 5010 as was mentioned. Juliana Furtado is the same bike. Pivot 429 or Mach 4. Any decent 120 travel bike from specialized. Canyon bikes are decent and inexpensive - again, that 120ish travel range. 2017 or newer. Should be findable around 2k. If she doesn't like it in a year or two she can sell if for 1,500+.
This is not her dream bike, just a gateway, and in two years she's likely looking to move on from this one either way. But she doesn't even know what she likes to ride yet, so that upgrade (ebike, longer travel, less travel faster, hardtail, same travel but nicer spec) can happen later once she knows what she wants.
Regardless, she better start kicking her BF's ass quickly or we'll be disappointed.