I suppose it's okay, though it does look rather dated. While I think Genna looks nicer than
Jenna, the spelling might be confusing for some people, and they might pronounce it as "GEHN-ə", so I'd pick
Jenna from the two of them.
Some combos:
Jenna / Genna
BernadetteJenna / Genna
EvangelineJenna / Genna
MagdaleneJenna / Genna
PenelopeJenna / Genna
Rhiannon