I thought the gal was grabbing at Ritsu because she's a loose woman, but she seems to want to touch everyone she likes/respects and just doesn't get personal space.
Re-reading this again, I think it's a bit overboard for Ami to hug Ritsu and get openly clingy like that knowing he already have a "girlfriend" and especially doing it in front of her. But eh, not the worse thing love rivals have done in romance manga's.
Though would be interesting if she already suspected it from the start and purposely try to snatch him and dig the truth out of them that way
but thankfully we later know Ami is too nice to do that lol