Yea, it would make me uncomfortable too. It's possible she's bi or lesbian but also maybe not.
I've known some women (I was never 'involved' with them) who were just very 'touchy feely' people. It's almost like they don't realize they are being that way and are possibly making others feel a bit awkward. At first I wondered at the possibility that they where hitting on me, but realized soon after that they weren't.
It did annoy me though. Unless your my gf/partner, I don't really want to be touched.
But saying 'I love you' 5 weeks in to a friendship is... from my perspective, weird.
If you want to make it clear to your friend that you aren't interested in women you could say it in an indirect way. During conversation you could mention a well known celebrity (you might have to 'steer' the conversation in that direction) who is lesbian/bi and then mention clearly that you could never be with a woman. That it's just not you.
I'm fairly certain that she would get your message.
I'll echo what Pug said. A lot of people are very touchy feely types, especially a lot of females i've encountered, which is fine, as everyone's different, but on the flip side there are people who like their personal space.
For me, I like my personal space. Unless the girl touching me is a a girl I'm interested in sexually/romantically, then I'm probably not gonna want someone touching me unnecessarily. To me it definitely seems a bit soon for her to be doing stuff like that and I don't blame you for being uncomfortable.
I hope all goes well with your message to her! I'm sure if you explained it delicately she'll understand.
I'm guessing she was quite lonely before you met her and just feels happy that you decided to be friends with her.
I'd say that instead of simply writing her off, you experiment with boundaries. Talk to her politely and calmly about the things that she does that make you feel uncomfortable, but that you'd still pretty much like to keep hanging out with her. If you do want that, that is. Also let her know that although you enjoy spending time with her, you also need breaks to be with other people, or with family, or just by yourself. Arrange for certain times for you two to meet up and hang out instead of letting her decide when to 'bother' you.