only way to tell is to take the engine tray off an have a look. if its all oily then yeh you have a leak.
if its not oily then leave her sat overnight with a peice of cardboard underneath her and see if there is any signs of oil on that in the morning.
if that dont work, same cardboard trick but have the engine running for 10-15 mins see if that makes her leak anything.
if it does you will either see smoke as it hits the hot exhaust and burns off or it will drip onto the cardboard and you will see it that way.
some twinspark engines drink oil, some don't use any, maybe just one of those things!
1999 156 1.8TS Sport Pack 3
2001 166 3.0 V6 24V Super
2003 156 GTA 3.2 V6 24V
2005 156 1.9 JTDM-Jet Sport
2008 159 1.9 JTDM Lusso
1997 GTV 2.0TS Lusso
2001 147 1.6TS Lusso