Well, I find the topic of falling in love with a non-human to be somewhat unusual, but I guess love is love. The thing about marrying something that cannot give consent however is a touchy subject, but at the same time, if somebody were to marry his or her cat, it's not like the cat would even know about it nor give a single damn about it.
There's a person I sometimes talk to on the internet who's a zoophile, and really, aside from the fact he really, really loves cats, if you get my drift, he's a perfectly normal guy and great to talk to. What I can tell from what he says is that the love is just as with any other form of sexuality, whether it be homosexuality, bisexuality, or pansexuality, love is love, and there's no need to keep "real" love inherently anthropocentric as the contrary is already known to be possible.
Just an FYI, while he may absolutely love cats, he does not have "giggety time" with them, because that would likely be bad for both the cat and his criminal record.
As for the fluid sexuality thing, I'd say, it can be fluid, but it's hard to say such changes occur within the course of a few days. I still can't randomly wake up in the morning and say to myself: "I am going to like boobs today!" while actually being genuine about it.