Lactose from cow's milk or other dairy cannot pass through into your milk. In fact, human milk naturally has lactose; the sugar in your milk that makes it sweet is lactose. It is more likely that she has a sensitivity to milk protein, which can pass through into the breastmilk. It would be wise to wait on introducing all dairy. As long as she's still nursing at least 3-4 times in 24 hours (and 5-10 min totally counts; older babies are very efficent and can drain the breast in under 5 min), then she doesn't need any other source of fat, protein, or calcium.

Good to know, eh?
It certainly doesn't sound like she's self-weaning.

It is quite normal for a todler to nurse less than an infant; some only nurse once a day at bedtime, but can keep this up for a year or two. You'll know she's self-weaning if she just gradually drops all the nursings sessions. Most babies won't self-wean before 18-24 mo.
One thing I wouls suggest is getting rid of the juice. It's filling her up on empty calories. Replace it with plain water or see if she'd like to bf at that time instead. Ds is 14.5 mo and still doesn't drink any juice; I personally drink it, but not really on a regular basis. Since it's not nessacary, I just don't see the point in giving it to him, especally since there are risks such as tooth decay and it has been shown to contribute to obesity in children!
Don't get me wrong; I'm not anti-juice. Like I said, I love to drink it myself. And it does have good vitamins in it like vit C. But it is mostly sugar (granted, natrual sugar) and water, with no fiber. Especally in young children, it can just end up taking the place of more nutritious foods.