No, it's not a summon! Essentially, in the world of The Ancient Magus Bride, the world is populated with fae/spirits/"neighbors", who lend their power to mages to perform feats of magic, such as, for example, lighting a candle, unlocking a door, allowing someone to fly, etc. This is pretty much entirely on the fae's terms, and they can outright refuse if they want, so Chise has no ability to summon them or bind them to her will or anything, it's literally the magical version of asking your neighbor for a cup of sugar for your cookies.

More detail can be found here and here if it helps, though the wiki is fairly sparse/incomplete.

I was assuming there probably aren't any fae or spirit-like creatures natively in the setting for Chise to commune with in order to do magic, so I was wondering if LILITH would draw in any fae with her for that purpose.