I would agree that you sound a bit unsure about what you want - if you were definitely against it I'm thinking you would have stopped it on the first occasion.
It's certainly certainly 'normal' (Sam's friend who isn't bf is also going through a phase and I was talking about it with his mum just on Friday).
I think if you want to stop it - sooner is better than later before it gets even more established. Does she have any other 'lovey' or security thingy you could substitute or introduce. 'Mummy and Kayla give teddy/dolly a special squeezy cuddle' and you could wear clothing that's difficult to access. When she tries - make a joke out of it, tickle her, offer substitute, say 'x (name of bf friend) has milk like this doesn't she, mummy and Kayla do special hugs instead'.
If you are getting engorged she's obviously being successful! If you do stop then watch carefully for signs of tenderness. You may even need to hand express a little to prevent problems.
You said
usually when she is upset or she gets hurt.
Sam sometimes asks for a bf at a time like this but I offer an alternative as I feel a bit funny about it being such an emotional crutch. I would prefer to comfort him in another way. That's just my personal decision. I would however say that I really feel Sam has benefitted from being an older nursling. I don't think I could have managed though if I wasn't 100% committed and although I'm aiming for self-weaning I don't think it's going to be easy.
You sound as though you made a real effort with breastfeeding. Please try hard to leave the unnecessary feelings of guilt behind. Focus now on what's best for you and her - it may be you want to join extended nursing land! - or it may be best to nip it in the bud now before she gets more attached to it as a support.
