Is it safe to inject Ellanse filler on an area that has had a small amount of botox injected 3 months ago?

I would consider it safe to treat with Ellanse in an area which had botox 3 months ago

How does it work
Polycaprolactone (PCL) is a medical polyester which has been used for medical purposes for over 50 years- found in sutures, orthopaedic implants and wound dressings. In the body, PCL is gradually broken down by hydrolysis into carbon dioxide and water by the body. The PCL microspheres used in Ellanse are designed to offer optimal biocompatibility. They have a smooth surface, a spherical shape and a size of approximately 25–50 μm
Carboxymethylcellulose (CMC) is a natural material derived from cellulose that is often used as a gel carrier for injectable collagen biostimulators (Ellanse, Sculptra, Radiesse). It functions to act as a medium for collagen biostimulator particles, and to provide short term volume replacement for 2-3 months.
Working together, the CMC gel delivers immediate results, while the PCL microspheres act as a biostimulator, to ramp up production of your own collagen over the next 2-3 months. This improves skin elasticity and creates a more youthful appearance.

Assuming that you have consulted with a clinician,
who has advised that this is something that they would recommend, I would agree
that this is a safe treatment. Botox typically lasts around 3-4 months, so I
would suspect that the effects of the may have worn off by the time of your
treatment.

Yes it is.Botox typically lasts 3-4 months.So if you Doctor thinks filler is a suitable choice to address your concerns, it should be OKAll the best

If your doctor thinks its a good idea then it likely is. Botox is most likely worn off after 3 months and even if it wasn't, I don't see how it could interfere with the filler's result.