Why would you say this? Mine was ~+5 (I upgraded it to +10 with her, because the firelink guy was gone). So why say this?
Fine that you feel the need to discredit what I say, but let me quote you this, then:
Players may encounter difficulty in finding Quelana, as there are requirements needed to fulfil in order to make her appear(she can appear even without fulfilling them). If players are unable to find her in her usual spot in Blighttown swamp, fulfilling the listed and confirmed requirements will make her appear:
Having a Pyromancy Flame+10* and above
Have not defeated Bed of Chaos
Note: Confirmed Quelana appearing even though Pyromancy Flame was only +2. Quelaag and Ceasless Discharge were beaten and the chaos covenant had been joined.
NEED CONFIRMATION: She did not appear for me until after Laurentius of the Great Swamp, whom you free from The Depths, and returns to Firelink asked me a question about the spell you got from Chaos Covenant in which I replied "Yes". He thanked me and then spoke of his master. Then he spoke of her. When I got to the Swamp again she was there. I had tried everything else suggested and this finally spawned her. If you can't find her try this and confirm f it works for you. This conversation is supposedly triggered by either getting that spell from the Chaos Covenant, or buying it from Quelana herself. IF he starts it and you say Yes, he will leave Firelink for good so be sure you have everything you want.
and..
‍‍‍Inconsistent Sightings:
It has been reported that she has shown up without any previous pyromancy training, after both defeating Quelaag, and discovering the Chaos Servant covenant (regardless of joining).
It was originally thought that she would only appear after having your Pyromancy Flame upgraded to at least +10, but player experience has disproved this as a constant.
It seems that she will permanently leave after the player has slain the Lost Izalith boss, the Bed of Chaos; or rather having defeated the boss prior to meeting her will prevent her appearance.
It is scarcely believed that Hollow Laurentius' existence in the area prevents her from spawning; or rather that after Laurentius is slain, she will appear.
Her spawning conditions are therefore still under dispute, however a map of her location can be found here: Drawing by chronoterra