Boyfriend's female friend friend likes him, and won't back off?

[M]

My boyfriend and I have been dating for 8 months, and we get along very well. We are both 23 years old, and serious about our relationship. We're also mature enough to accept and understand our friendships with former love interests as long as we aren't flirtatious with them, and they're aware that we're committed to one another. He told me about one of his female friends, and how they used to like one another - and how she recently found out about him dating me (we were keeping our relationship on the down low initially).

Nonetheless, ever since she found out about us - she's been all over his facebook/instagram. Prior to this, I had never seen her on his Facebook or Instagram at all. But now, she'll be the first one to comment on every post, and picture. If he posts a picture of himself with his male friends, she'll be like "can I join you guys?" etc etc. My boyfriend responds to her with very dry answers and has even given me the privilege to go through his phone or Facebook if I feel the need to do so; however, that doesn't stop her from continuously bombarding his profile. I know I shouldn't let petty stuff like this on Facebook and such get to me; but I think it's pretty clear that she still into my boyfriend. Whenever I read her wall posts, I end up getting frustrated with my boyfriend. How do I deal with this?