There are no flights from Milan MXP to Florence. There hasn’t been one for almost 20 years since Alitalia abandoned Malpensa as their hub.
I don’t know how things will be in August but currently there are no flights from Rome FCO to Florence either. But even in normal times, pre-pandemic, Alitalia only had 3 a day in each direction. Given the fact that I don’t expect things will be back to normal within 3 months I don’t expect those flight to resume that quickly. Alitalia is in dire financial conditions, and as part of the deal between the Italian government and the the EU Competition Commissioner to allow for another government loan, Alitalia will become a new company called ITA. The Alitalia trademark will be sold on an auction. ITA will have to reduce its fleet (and staff) by 50%, therefore I’m not even sure they will ever resume those 3 flights, which were never full anyway.
Covid free flights are currently offered by Delta/Alitalia but only on the following flights:
JFK-MXP
JFK-FCO
ATL-FCO
Any other flight option, at the moment, requires a 10 day quarantine upon arrival. We don’t know about August of course.
There are no Covid free flights offered directly from LAX at this time. The only Covid tested flight currently are from ATL or JFK.
Given the current circumstances, the best option for her is to fly via those two US airports, to Rome FCO (Milan MXP is a bit farther from Florence).
From Rome FCO airport she can take a train from the airport to Florence, with a train change at Roma Termini or Roma Tiburtina, Rome’s main stations. That would be the fastest option (about 2.5 hours from the airport, including train change in Rome), at a cost of about $75 per passenger (full price in standard class). There are also 2 trains (one shortly after 11am and one shortly after 3pm that go directly from the Rome airport to Venice (stop also in Florence) that require no change. Not sure if they are operating at this time. However the vast majority of train departures from the airport to Florence require a change at the aforementioned stations downtown Rome. There are two every hour, so plenty of choices.
A limo service would be very expensive (about $600 for 3 passengers), although very convenient if they have a lot of luggage. Driving time is about 3.5 hours.
Another option (the cheapest, although driving for 3.5 hours while jet lagged is not ideal) would be to rent a car and drive themselves.