so you want to force this faerie to come to you when you call to it because you want to be its friend?
i wouldn't summon a faerie, i would try either meeting this faerie at night, or try welcoming faeries to your home so one might visit. faeries can be nice, but they can also be very spiteful so you might not want to force a fae to do something. try leaving out some milk and honey as an offering [if you have a garden place it there] usually i saw faeries at my old house late in the evening. i don't work much with fae so i don't know when they're out more, but if they're usually out at night, try figuring out a night where you could sleep over at your friends and she could introduce you. [keep in mind you may not physically see the faerie, it might be an orb out of the corner of your eye, or a feeling of its presence]
To add to what Nekoshema said, no spell is 100% guaranteed to work no matter how skilled the magic user might be. There are many things which can cause a spell to not work as intended or to not work at all.
2. why do u want to befriend some1 who u said was ur friend already?
3. if u know she will be there, then why call upon her?
no offence, but just because u dont have beter things to do, doesnt mean she doesnt. should she return, u could just ask her to visit more often, right?
I don't believe you have to actually summon them. :)
It seems you are friend with that Fairy and want to spend more time together.
So next time they come, ask her/him you want to be friends and you want to spend more time together because you really like them. Speak words by heart, and they will understand.
Ask for their name, and it seems you don't know Fairy's name either. Time to meet each other. :)