SQL Server can be a memory hog. The free Express Edition less so.
Of course you can stop the SQL Server services when you're not using the app, then they are not running and don't take up any memory or cpu. You can write a small batch file to start and stop the services (search online for "net start batch file").
If this is not an option for you, then the next step would be to ask the data provider to give you the data in another format such as ACCDB or XLSX or CSV.