What GG said, and also, do not expect her, or any woman, to be your unicorn, that is, into both you and your bf sexually and romantically equally. You can't force that, and more often than not, attempted planned triads go quite badly. If you do want her, let her know, and see what she says. Let bf stay out of it for a while until if and when you and she are solid in relationship.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
There's no lying in polyamory!
I'm a 58 year old woman with 2 partners:
miss pixi, my live-in gf, 36 (together since Jan '09)
Ginger, bf, 61, married, lives nearby (together since Jan '12)