No and No.
For all genders masturbation is normal (as is not masturbating). Some adults use porn for stimulation during masturbation. So it's common, though if I'm honest not always advisable, for adults to look at pornography while masturbating for both genders.
As an aside just remember that the values in porn can be highly dubious, the sex fake and the bodies artificial. If you see it in porn it's unlikely to be representative of normal sex or relations.
The internet and internet porn's really opened the door for people to explore their sexuality. The idea that sexuality is limited or binary to a homosexual or heterosexual outlook is hugely flawed. Sexuality covers the full gambit of sexual desires and tastes - covering everything from inanimate objects, to certain body parts, fantasies, abstract things like colours and shapes, feelings, sensations, plots and traditional areas relating to gender, etc. So I find it totally normal for someone to look or fantasise at things that they have no interest in real life.
Some other scattergun points:
* Lesbian porn tends to be easier to engage with and naturally more female focussed than mainstream heterosexual porn.
* There's also associations to consider, if you associate a vagina with feeling sexual then naturally you may be stimulated by looking at vaginas. You can also relate to the feeling.
* There may also be the taboo angle, where the sexual arousal is about looking at material that is somehow taboo, eg someone who does not identify as a lesbian looking at lesbian porn.
One's sexuality fluctuates and changes over time. You are always you, so don't fence yourself in or worry about it.