Unless you shoveled it, no.
As you say its public, they are there your friend isn't they have the right to the spot. Doesn't matter how long your friend is going to be even if they're right behind them, they have right of way by being first to a first come first serve spot.
If I were your friend I'd ask you not to do this unless there some sort of urgency (e.g. being kicked out), or medical reason for which them having a closer spot matters. Otherwise walking a little isnt an issue.