I would just say that in April Lisbon airport was considerably busier (even at 5:30am) and therefore much slower than I had expected for a departure flight to LHR. This was not due to any strike or work slowdown on the date I was there. Also not laid out particularly well. 1.5 hrs would be tight. That said, it's more worth the risk on her way TO Italy than on the way home, because there will be more intra-European flights that she can be accommodated on if she misses the connection. Going back home, she likely has fewer TA options and if she misses that, it may mean extra stop(s) or waiting until the next day.