Hi and welcome!
How old are your two girls and how long have they been together? And how long has th aggressiveness/clinginess been going on? It is difficult to judge what exactly is going on without a bit more background information, as similar behaviour in sub-adult sows will have to be read differently.
It can be a sign of a small growing ovarian cyst in a mature sow and it would be good if you had her checked by a piggy savvy vet if that is the case with yours. There are now less invasive alternative treatments to a major spaying operation available, like a course of hormones or draining the cyst. We have got a recommended vet locator on the top bar for our UK members.
Please make sure that your girls have two bowls, water bottles, hay racks or corners and hideys (ideally with two exits). Each item should be at least a body length if not more away from the other same item, but best at each end of the cage. Feed smaller portions more often, so food raids are minimised and have a bit extra in hand. Weigh your undergirl once daily at the same time in the feeding cycle to make sure that she is getting enough to eat instead of the usual weekly check-p weigh-in. The daily variance can be as much as 30g due to a full/empty bladder/tummy; you want to eliminate that as much as possible.
As we have members from all over the world, we find it very helpful in adapting any advice and recommendations to what is actually avaible or possible where you are, if you please added your country, state or (for the UK) your county/city. Click on your username on the top bar, then go to personal details and scroll down to location. Thanks!