Hello shirleybell
You can find the schedule using the SBB trip planner on www.sbb.ch/en. Simply enter FROM: Basel EuroAirport TO: Interlaken Ost, and it will give you the entire connection. We have an integrated public transport service here, the trip planner knows all the possible connections. There is no need to check multiple sites for the schedule. However, with an arrival at 23:05 (11:05 PM), she will not have any connection to Interlaken. The last possible connection is at 22:26 (10:26 PM). She might have to stay in Basel for the night.
Also, Basel EuroAirport is known for long queues in front of the customs. Depending on the number of passengers arriving at the same time, the waiting time can easily take 30 minutes.
At Basel Airport, which is on French territory, getting through the airport basically means getting past the French customs. The French want to know who arrives, no matter the passengers’ departure destination. For the Swiss exit, she will have to go through the entire hall, to pass Swiss customs. There is bus no. 50, a green bus, that will take her to Basel SBB station. The bus stop is right at the entrance and this at both, Basel Airport and Basel SBB train station. From the latter she will have direct trains to Interlaken or with a change - depending on the time of travel.
Kind regards,
Roland