Some babies never take a bottle. Mine didn't. At 6 months, yours is probably in a growth spurt, needing extra feeding to get the nutrition to support that. It will most likely pass in a couple weeks or a month. If she's ready, you could try offering more solids, but it will be a while before she's taking substantial enough quantity of solid food to make a difference in her nursing. Milk is still the primary food pretty much all the first year.
I think she's perfectly normal. Personally I would never want to wean from breast milk, even to formula, until at least 2 years (my oldest nursed until past her 4th birthday, the younger is 2 and still nursing). I would first look for other ways to work with her needs and satisfy yours as well. What kind of work are you doing, and is it possible you can do it while she nurses? Eg, if you're at a computer, maybe a good carrier would enable her to nurse while you work. Do you have a helper who could play with her? If she's actively engaged in a bouncy or with a person holding a pretty toy or in tummy time . . . maybe it could stretch the time you get to work, for a little bit.
As for letting her cry, or trying to force her to take a bottle, in my opinion it begins a pattern of having an antagonistic relationship in which the biggest person wins. I don't prefer to parent that way. That's my 2 cents.