In my opinion, it's perfectly ok to let her do this, even though it's hard on you. She will grow out of the need to do this. However, The No Cry Sleep Solution by Elizabeth Pantley is an excellent book on helping your child sleep longer. YOu could try things such as patting her back or bottom, but I personally don't think you should let her cry.
Eating solids three times a day is a lot for a 5 month old. Perhaps she is stocking up on breastmilk at night. Make sure you are nursing first, then giving solids. Solids aren't the form of nutrition she needs...they are only for experience, and aren't enough nutrition anyway. So her main form of nutrition should still be breastmilk until she is 1 (at least).
I also think it is very typical of this age to wake at night, despite what "sleep experts say" about her being "physically capable" of STTN.
The breast isn't just for food, either. It's comfort, and it will help keep up your supply when she comfort nurses like that. I personally think that the breast was made to be so comforting for a reason. Why else would pacifiers be shaped nipple-like? Pacifier companies chose the nipple shape for a reason - it is the most comforting thing and their little mouths are made for the shape.
Ultimately it is about what works best for your family, but if you are ok with her waking several times, don't worry about what anyone else says. My son did that, too, and weaned himself of it eventually. She won't be doing this always! GL!