Welcome to the forum,lovesticklin.
In answer to your question, while I usually dont like to use the word "normal", I will say that I have heard from straight females I know, that enjoyment of F/F tickling among straight females is in fact very common. I was talking to a female friend about this once, and her theory is that F/F tickling among straight girls, is almost an accepted social norm, as girls are very touchy feely, even toward each other, even if they are straight. Guys, on the other hand, except for a bear hug, or a pat on the back, dont have this accepted social role. It is usually assumed, that if a guy wants to tickle another guy, that he is either bi, or gay, even though we all know this isnt always the case.
I may be oversimplfying it, but this is what I've heard, and seen, at least.
Mitch