Like this post?
sure can, but it depends on a lot of things.
if she has an intact hymen, fingering her may break it, and you may end up causing her some discomfort and perhaps bleeding.
if she does not (it can break from a number of things other than just sexual activity) then you're in the clear.
a good bet is to find out if she wants you to in the first place. if she does but is unsure of whether it will hurt or not, suggest to her that she try doing it herself when masturbating some time, just to make sure. that way, if shes never been fingered/done it herself/her hymen hasnt been broken from some sort of nonsexual physical activity, then she can take it slow, do it in as much comfort as possible with as little embarassment as possible, and get the painful part over with in privacy.
personally, if i were in your shoes and she was comfortable with it and wanted me to proceed, i would be quite pleased to do so, even if there was a little bit of blood.