False ally

• Supporter to keep a watchful eye on
• Rival one is amicable with
• Faux ally
• Portmanteau for a false ally
• Semi-opponent
• Rival who's somewhat on your side
• Bud that you're not always high on?

Wikipedia Word definitions in Wikipedia
"Frenemy" (less commonly spelled " frienemy ") is an oxymoron and a portmanteau of " friend " and " enemy " that can refer to either an enemy pretending to be a friend or someone who really is a friend but also a rival . The term is used to describe personal, ...

Wiktionary Word definitions in Wiktionary
n. 1 (context humorous English) Someone who pretends to be your friend, but is really your enemy. 2 (context humorous English) A fair-weather friend who is also a rival.