<human>: Summarize the given text in a few sentences.

We're almost at our wit's end with these two cats and really do not want to have to re-home our new cat.

We picked up a stray in April that had been hanging out near my work, and after a brief stay at the humane society we decided to adopt her.  She is a 1.5 year old female, and a pretty big girl, probably about 10lbs (in fact, she was so well fed despite being out on her own that we thought she was pregnant). She's an  friendly and confident cat who loves meeting people and is super inquisitive (if not the brightest). Our other cat, on the other hand, is a bit more reserved. She is now 6 years old and more petite and timid. She's been with us since she was 2 or so and is used to being the only cat in the house.

When we first brought the new cat home, we kept them in separate rooms and used feliway spray.  We then started to try to do feedings on opposite sides of a door, but during one of these early feedings they caught sight of each other and Muji (the older) immediately hissed.  We backed off for a bit and then reintroduced feedings separated by a door as well as doing some side-switching so they could get used to each other's scent. 

We've been working on the two of them now for almost four months, and we've gotten to the point that they can eat separated only by a baby gate without much problem.  But as soon as the food is gone, the older cat will hiss and the younger cat will swat at the gate and we're back to square one.

We try to play with them every day using Da Bird so they do get some excitement (they're both indoor cats) and exercise to tire them out.

Any advice?
Has any one gone longer than this and actually had success integrating a new cat? I know it wasn't the greatest idea to try this with two adult females.
<bot>: unsuccessful integration of a new adult female cat into a house with an older adult female cat despite 4 months of trying. need advice